One 10.25 oz package of brownie mix, prepared according to the package directions will yield 17 cupcakes if you put 1/8 cup batter into each paper liner. That results in a decent layer of brownie as the crust. Feel free to use the entire batter for 12 thicker brownie cheesecakes, but you’ll have less space for cheesecake batter.
Stir ½ teaspoon of melted chocolate into the unbaked cheesecake batter, then bake them for 30 minutes. I used white chocolate chunks, but would recommend for visual appeal and flavor that you use chocolate chips or chocolate/ peanut butter/ butterscotch chips.