01 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
02 - In a large mixing bowl, combine the brownie mix, eggs, vegetable oil, and water. Stir until a thick, sticky dough forms.
03 - Scoop out tablespoon-sized portions of dough and form into balls. Roll each ball in granulated sugar if desired.
04 - Place dough balls 2 inches apart on prepared baking sheets.
05 - Bake for 9 to 11 minutes until cookies are set around the edges but still soft in the center.
06 - Immediately press a mini peanut butter cup into the center of each warm cookie.
07 - Cool cookies on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.