Begin by pre-heating the oven to 425°F (220C/200C Fan).
Line a baking sheet with parchment paper and place one rectangular sheet of puff pastry on the sheet. (see note)
Spoon out dollops of cookie butter and use an offset spatula to spread out evenly over the full sheet.
Place the second puff pastry sheet over top and press gently to sandwich together. (see note)
Using a knife, lightly trace a basic tree outline into your puff pastry. Start from the centre of the top short side, drawing a long triangle down, to points about 2" up from the bottom short side. (see note) This will give you space at the bottom for your tree trunk.
Trace a tree trunk about 1.5" wide overlaying the mid-point of the bottom short side and rising up to the line with the bottom of your tree.
Once you're happy with your tree outline, cut away the excess pastry, reserving this for decoration.
Lightly score lines up from the sides of your trunk (making a long rectangle over the centre of your tree) - these will provide guidelines for when you slice your branch segments.
Cut straight lines in from the outer edge of your tree to the guidelines on each side (leaving the core of the tree intact) to make segments or 'branches'. Each should be about 1"-1.5" wide. (see note)
Once segmented, twist each branch one or two times to give the swirl of Biscoff and pastry.
Using excess pastry, cut out a star to place on top of the tree (see note).
In a small bowl beat your egg and then brush this over the pastry.
Bake in the centre of your pre-heated oven for about 20 minutes, until puffed and going golden on top.
Once baked, remove from the oven, dust with powdered sugar and serve.