Pre-heat oven to 350°F andline a baking sheet with parchment paper.
In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter and 1/2 cup of sugar.
Crack the egg and add the vanilla, mixing until fully incorporated
Add the flour, cream of tartar, baking soda, and salt
Mix until it all comes together
On a small plate, mix together the 2 tablespoon sugar with the cinnamon
Using a cookie scoop, (I used a 1 1/2 tablespoon size), scoop out a ball of dough
Divide the dough into two, rolling each piece into a ball then slightly flattening into a disk-like shape.
Spoon about a teaspoon of Biscoff in the middle of one of the ‘disks’ of dough.
Place the other one on top and pinch the sides together so that the cookie butter cannot be seen.
Roll into a ball and roll around in the cinnamon-sugar mix fully coating the outside.
Place on the baking sheet about 2 inches apart, and continue the process with the remaining dough.
Bake for 10 minutes. Remove from the oven and allow to rest for 2-3 minutes before transferring to a cooling rack. Enjoy!