Begin by heating your full fat milk to 104°F/40C (see note).
When your milk is at the desired temperature, add your yeast and 1 teaspoon of your sugar. Stir together lightly and set aside for 10 minutes until the yeast becomes foamy (see note).
In the bowl of a standing mixer fitted with a dough hook, add your flour, bread flour, salt and remaining sugar. Stir together.
Once the yeast is frothy, add this to the flour mixture, immediately followed by two eggs and one egg white. Reserve the egg yolk in a small bowl for later (see note). Begin mixing on a low speed until a dough forms and continue until it begins to pull itself away from the sides of the bowl (about 15 minutes).
After 15 minutes, begin adding the softened butter a tablespoon at a time, allowing the butter to be incorporated into the dough.
Once all the butter is added, continue mixing on a low-medium speed for a further 12-15 minutes until the dough again pulls itself from the sides. It will be a softer dough now that the butter is added.
While the dough is being kneaded, grease a clean bowl with butter.
Scrape the dough into the greased bowl, cover with plastic wrap and set in the refrigerator to slow proof for about 8 hours (or overnight) until doubled in size.
Following the first proof, prepare a clean work surface by dusting with flour. Turn the dough out and knock it back. Gently pat this into a square and use a rolling pin to roll out into a 12" x 12" square.
Dot softened butter over the surface of the dough square and spread to cover.
Stir together the brown sugar, cinnamon and chopped pecans. Sprinkle this over the butter and then tightly roll the dough into a log.
Use either a sharp knife or some flavourless dental floss to cut the log. First trim about an inch or two off each end to remove uneven bits. Then divide the dough into 9.
Line a square baking pan with parchment paper and place the 9 cinnamon rolls inside. Cover with a clean kitchen towel and allow to proof for a second time - this time for 2 hours at room temperature.
When the 2 hours is nearly up, preheat your oven to 350°F (175C/155C Fan).
Add a tablespoon of milk to the reserved egg yolk and beat with a fork to combine. Brush this over the top of your cinnamon rolls.
Place the baking pan in the middle of your pre-heated oven and bake for about 20-25 minutes, until golden on top.
Remove from the oven and allow to cool for about 10 minutes, while you prepare the icing.
To make the frosting, whisk together the powdered sugar, spreadable cream cheese and vanilla. Slowly add the milk about a teaspoon at a time until you reach your desired consistency.
Spread the frosting over the buns and serve.