1. Cream together the butter, sugars, and vanilla.
2. Add the egg and Biscoff and beat again. Sift together the salt, baking soda, 1 cup flour, and cornstarch. Slowly add to the creamed mixture.
3. Remove 1 cup of cookie dough and set aside.
4. Add the extra 1/4 cup flour to the remaining cookie dough in the bowl.
5. Roll into 20 even dough balls and place in the refrigerator.Take the reserved cookie dough and stir in the cocoa powder and milk until mixed. Stir in the chocolate chips gently.
6. Roll into 20 even dough balls and place in the refrigerator. Refrigerate the cookie dough balls at least 30 minutes.
7. Remove the dough from the refrigerator.
8. Roll one Biscoff ball with one chocolate ball. Slightly flatten each one together, then roll into a ball. Repeat with remaining dough balls.
9. Place cookie dough balls on a baking sheet and bake at 375 degrees for 8-9 minutes.
10. Remove from the oven and let sit on the hot baking sheet for 2 minutes before moving them to a piece of parchment paper on the counter.
11. Let cool completely. Store in a sealed container. Makes 20 cookies.