Combine the butter and both sugars in the bowl of a large stand mixer. Mix with a paddle attachment on medium-low speed until well-blended, but not light and fluffy. You don’t to beat too much air in to the dough, because that will cause it to spread.
Add the egg and vanilla extract, and mix well. In a small bowl whisk together the bread flour, cocoa powder, baking powder, and salt. With the mixer running on low, add the flour mixture and mix until all the flour streaks disappear. Stop the mixer, add the miniature chocolate chips, and stir them in by hand. Scrape down the bottom and sides of the mixing bowl very well with a spatula. Wrap the cookie dough in cling wrap and chill for at least 2 hours, until solid. (The chilling time and the later time in the freezer are both important, so don’t skip them!)
Once the dough is chilled, preheat the oven to 375 F. Turn two muffin tins upside down. Cut foil into 5x5-inch squares. Press a square of foil on top of the bottom of a muffin cup, shiny side up. Press foil around every other muffin cup (you’ll only be using half of the cups, so that they don’t bake into each other). Each upside-down muffin tin should have 6 muffin bottoms foiled. Spray the foil with nonstick cooking spray.
Divide the dough in half, and keep half in the refrigerator while you work with the other half. Lightly dust two sheets of waxed paper with flour, and roll the dough out between the waxed paper until it is 1/8-inch thick. This recipe works best with a very thin layer of cookie dough, so don’t let your dough get too thick. Use a 3.5” or 4” circular cutter, and cut 6 circles out of the dough. Lift the dough from the waxed paper with a spatula, and drape it over the foil-covered muffin cup. Press it gently on top and on the sides of the cup. If there are any cracks, smooth them out with your fingers. The dough will move down a little while baking, so no need to press it all the way down to the bottom of the cups.
Put the tray in the freezer to chill for 10 minutes while you repeat with the remaining dough. Bake the cookie cups for 12 minutes at 375. Let them cool completely before sliding them off the muffin bottoms. Gently peel the foil from the inside of the cups. Fill with ice cream, mousse, whipped cream, pudding or whatever else you’d like!