The ultimate Oatmeal Sandwich Cookies! This easy recipe for oatmeal and marshmallow cookie sandwiches is essentially a copycat of Little Debbie's Oatmeal Creme Pies. Super soft and chewy spiced molasses oatmeal cookies sandwiched together with a light and airy marshmallow fluff filling.
Why these work
- Inspired by Little Debbie's famous Oatmeal Creme Pies - these sandwich cookies are directly based on the American lunchbox classic! Combining classic oatmeal cookies with a marshmallow-y buttercream filling.
- Soft and chewy molasses oatmeal cookies - an easy oatmeal cookie recipe made with melted butter and molasses, makes these super soft and chewy sandwich cookies.
- A quick copycat creme pie filling - my simple marshmallow fluff buttercream brings these sandwich cookies together with plenty of fluff and flavour.
To make my soft oatmeal sandwich cookies, you'll need
- Butter - unsalted butter, melted. You can substitute with salted butter for this recipe, but salted butter will add extra salt to the overall flavour, so you may want to decrease the additional salt added.
- Molasses - or dark treacle. This will give your cookies a cozy flavour and help to create a chewy texture.
- Sugar - granulated sugar or caster sugar.
- Light brown sugar - sometimes called muscovado, firmly packed. Using brown sugar will add to the molasses notes in the cookies. You can use dark brown sugar here, but I find it overpowers the sandwich cookies with molasses, which takes a little away from the light and fluffy filling.
- Egg - a large egg, ideally at room temperature for adding to the dough.
- Flour - all purpose flour or plain flour work in this recipe.
- Baking Soda
- Rolled oats
How to Make Oatmeal Sandwich Cookies
This is really a one-bowl recipe.
- Start by melting the butter in a small saucepan along with the molasses.
- Then whisk the butter mixture into the sugars and beat together until fully emulsified (about 2 minutes). (image 1 below)
- Add the egg and vanilla, beating to combine.
- Next add the flour, baking soda, salt and spices. Whisk until just combined. (image 2 below)
- Add the oats and stir together into a dough using a spatula or wooden spoon. (image 3 below).
- Spoon the runny oatmeal cookie batter well spaced on a piece of parchment or silicone baking mat.
- Bake in the centre of a preheated oven for about 8-10 minutes until the edges just start to darken.
- Remove from the oven and allow to cool for a few minutes on the tray before transferring to a wire rack to finish cooling.
Softened Butter versus Melted Butter
The consistency of butter matters in baking.
In most cases, you want room temperature ingredients (including butter) so that these mix well together and bake evenly. For cookies, for example, room temperature butter helps keep cookies from spreading too much. In fact, many recipes will suggest chilling the scooped dough before baking, to reduce the spread even further and produce nice thick and chewy finished products. This is the same logic for pastry crusts like my All Butter Shortcrust.
The style of a knock off Little Debbie's Creme Pie demands something a bit different. The goal here is actually a thin cookie, with a bit of a soft bendy finish. This means melting the butter is key.
Melting the butter before using it produces a wetter dough and encourages more spread when baking. The result is a softer thinner final biscuit.
The filling for a classic oatmeal cream pie is a bit of a contentious question. Many recipes will simply call for a well whipped vanilla buttercream. But, for me the Little Debbie's original has a marshmallowy quality, that demands a bit of marshmallow in the filling.
My marshmallow buttercream is quick and easy to whip up with the following:
- Butter - unsalted butter, softened at room temperature. It is important that this is unsalted for the filling to avoid excess saltiness in these cookie sandwiches.
- Powdered sugar - or icing sugar. It is best practice to sift this for a buttercream to give yourself a smoother creamier finish. It is particularly important to do this if yours is especially lumpy, otherwise you will end up with small clumps of powdered sugar in your final icing.
- Marshmallow fluff - a bit of marshmallow cream goes a long way to flavouring and adding a fantastically sticky fluffy texture here.
- Vanilla extract
- Milk - I like to use full fat or whole milk when baking. It gives that extra little bit of rich creaminess. For this buttercream, you can use 2% or semi-skimmed, but I would recommend against 1% or skimmed milk as it tends to be too watery.
Making this marshmallow buttercream is very similar to my standard American buttercream recipe, with one big exception:
You want to whip or whisk the ingredients here - don't worry about adding air. In traditional buttercream, you aren't looking to whip the ingredients into something fluffy as this can cause air bubbles in decorating. For this cream pie filling, you do want a light and fluffy finish.
- Start by using a handheld electric beater to beat together the butter, marshmallow fluff and powdered sugar. Be careful as the thickness of the fluff might initially make beating difficult, but once this is incorporated it will begin to be smooth.
- Add the vanilla and the milk last to form a light and smooth frosting.
- Tip: You can add extra milk if you feel your frosting is too thick or more powdered sugar if you feel it is over runny.
Assembling Oatmeal Sandwich Cookies
Once you have your cookies and cream, you need to assemble the oatmeal cream pie. This is best done with a piping bag.
- Start by filling your bag with the frosting and then cutting off the tip so that you have about a ½" opening.
- Pipe onto the flat base of one of your oatmeal cookies.
- Sandwich this with the base of another cookie.
- Repeat this process until you have paired all of your cookies into sandwiches.
- Cookie sandwich sizes - this recipe makes about fourteen average size cookie sandwiches, or seven giant oatmeal cookie sandwiches. For the giant oatmeal cream pie, I used an OXO #40 Good Grips dough scoop. This dollops out about 1.5 tablespoons of batter, which spread to large cookies. If you want to make smaller cookies, you can either use a smaller scoop or a kitchen spoon to portion these. As the dough is very wet, they will spoon out and spread easily.
- Different filling - this recipe is essentially a copycat of the Oatmeal Creme Pie of Little Debbie fame. These use a marshmallow-y vanilla filling and therefore the filling here is marshmallow based. You can absolutely use a different filling for your oatmeal cookie sandwiches! Try Cinnamon Buttercream, Dulce de Leche Frosting or maybe a Rum Buttercream with chopped nuts like in my Gingerbread Cookie Sandwiches.
- Play around with spicing - oatmeal cookies are a great cookie dough to spice up to your own taste preferences! I'm a huge cinnamon fan, but if you like ginger or maybe want to add pumpkin pie spice, you can add a bit to the dough in these cookies.
- Add nuts, raisins or chocolate chips - you can add a bit of extra texture and flavour to these cookies with chopped nuts, chocolate or dried fruit, such as raisins. Pecans in particular go nicely with these cookies, just be sure to chop them up into small pieces for adding to the dough.
- Dairy free - you can substitute the butter in the cookie dough for a flavorless oil or a dairy free butter substitute and will get similar results. As there is no milk in the cookie, you will not need to make other substitutes to achieve a dairy free oatmeal sandwich cookie. You will, however, need to make further alterations to the filling, such as using a non-dairy butter or shortening.
Expert Baker Tips
Tricks for Thin, Chewy Sandwich Cookies
So, one of the trademark elements of the classic Little Debbie's Oatmeal Creme Pie is the super soft thin oatmeal cookie. This can be difficult to recreate at home, especially when most cookie recipes encourage you to aim for a thicker biscuit.
There are a few key tricks to making these soft thin cookies:
- Use melted butter, not just softened.
- Whisk the sugars, molasses and butter together until fully incorporated. The butter will initially try to separate from the sugars, but with a bit of whisking this will all come together as the sugars begin to dissolve into the butter.
- Avoid over-baking and take these out as soon as they start to golden at the edges.
- Let the cookies cool for five to ten minutes on the baking tray before removing to a wire rack. This makes for a chewier cookie than if they are immediately transferred to the rack.
Advice for Assembly
- Always pre-pair your cookies when sandwiching. There is no better way to be prepared than to pre-pair! (I couldn't resist...). Anyway, matching up your cookies before you begin to fill means that you have the best chance of ensuring nicely even cookie sandwiches and you know exactly how far your filling needs to go.
- You don't need special equipment for filling your cookie sandwiches. If you don't have a piping bag, you can make your own DIY piping bag with any square or rectangular plastic bag. Simply fill this with your frosting and cut off a corner as you would cut the tip of the piping bag.
Mixed spice is a British blend of warm spices, like cinnamon, nutmeg and allspice. If you don't have access to mixed spice, you can use your own blend of nutmeg and allspice to accompany the cinnamon in this recipe, or replace with pumpkin pie spice, which is a similar blend.
These oatmeal creme pies last comfortably for a few days at room temperature in an airtight container. If you have slightly over-baked your cookies, they can in fact improve with a day or two as the cream filling will help to soften the cookies a bit, making them chewier.
Yes, you can freeze these oatmeal cream pie style cookies. If doing so, assemble as directed and then transfer to a freezer safe container.
For best storage, I would recommend flash freezing them first. Place the cookies in a single layer on a lined tray and freeze for a few hours until firm and frozen. These can then be wrapped individually before stacking for a more efficient freezer friendly storage.
Allow to defrost before eating.
If you like this recipe, check out some other oatmeal favorites:
- Edible Oatmeal Cookie Dough
- Oatmeal Coconut Chocolate Chip Cookies
- Date Filled Oatmeal Cookies
- Classic Oatmeal Cookies
- No Bake Cookies without Peanut Butter
- Oat Crumble Topping
Oatmeal Sandwich Cookies
Soft Oatmeal Cookies
- ¾ cup unsalted butter
- 1 tablespoon molasses or dark treacle
- ⅓ cup light brown sugar firmly packed
- ¼ cup granulated sugar or caster sugar
- 1 large egg ideally at room temperature
- ½ teaspoon vanilla extract
- ¾ cup all-purpose flour or plain flour
- ¼ teaspoon baking soda
- ¼ teaspoon salt
- 1 teaspoon ground cinnamon
- ½ teaspoon ground nutmeg
- 1½ cups rolled oats
- ½ cup marshmallow fluff about ⅓ of a jar
- ½ cup unsalted butter softened at room temperature
- 2 cups powdered sugar sifted
- 1½ teaspoon vanilla extract
- 1 tablespoon milk
Instructions for Oatmeal Cookies
- Preheat an oven to 350°F (175C/155C Fan) and line baking sheets with parchment paper or silicone baking mats.
- Place the butter and molasses in a small saucepan and cook over a medium heat until the butter has melted.
- Place the sugars in a large bowl and add the melted butter mixture, whisking together until well combined.
- Add the egg and vanilla to the bowl, whisking to incorporate.
- Next, add the flour, baking soda, salt and spices. Whisk together until just combined.
- Add the oats and mix with a spatula. The dough will look quite wet, but this is to be expected.
- Spoon the cookie dough onto prepared baking sheets, either using a spoon or a cookie scoop. These will spread, so separate them well.
- Bake in the pre-heated oven for about 8 minutes, until the edges begin to turn golden. Watch carefully to avoid overbaking. Remove from the oven and allow to cool for about 5 minutes on the tray before transferring to a wire rack to cool completely.
Instructions for Marshmallow Fluff Frosting and Assembly
- In a large bowl using an electric hand mixer, beat together the softened butter, powdered sugar and marshmallow fluff until a thick cream. Add the vanilla and milk, beating to combine.
- Pair up your cookies, so that you have matching pairs of two similar sized cookies. Add the marshmallow buttercream to a piping bag and pipe this onto the base of one of the paired cookies, sandwiching together with the other. Repeat until finished sandwiching all pairs.