Preheat oven to 350°F. Line your muffin tin with cupcake/muffin liners.
In a large mixing bowl, add ingredients. Mix with a whisk until smooth, uniform batter forms.
Fill cupcake liners 2/3 full with batter. Bake for about 22-24 minutes, until muffin tops puff up, look completely cooked (no longer liquidy or jiggly), and knife inserted comes out clean. Muffins will initially puff up like souffles. If you remove them before they are finished cooking they will deflate significantly. If you remove them after they are cooked, they should only deflate slightly. To decorate, you can make a small slit in the center and put half a biscoff cookie in each one.
The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.