In the bowl of a stand mixer, cream together the butter and both sugars until light and fluffy. Add vanilla and egg and mix until smooth, scraping the bowl as necessary.
In a separate bowl, sift together the flour, cocoa, baking soda and salt. Gradually add the flour mixture to the butter mixture until incorporated. Fold in the mini chocolate chips.
Line a baking sheet with parchment paper. Spoon 1 tsp sized cookie dough balls onto tray, about 2-inches apart.
Bake 7 minutes or until puffed and just set.
Let cookies cool for 1 to 2 minutes on the baking sheet, then place 2 YORK MINIS in between 2 warm cookies. Place cookie sandwich on a wire rack to continue cooling. Repeat with remaining cookies. Gently press cookies together as the chocolate melts, helping the cookies stick to the peppermint patties. Enjoy!