1) Preheat the oven to 375°F. Lightly grease (or line with parchment) two baking sheets.
2) In a medium-sized bowl, whisk together the flour, cocoa, baking soda, and salt.
3) In another bowl, beat together the sugars, butter, and peanut butter until light and fluffy.
4) Beat in the vanilla, egg, and water, then stir in the dry ingredients, blending well.
5) Stir in the mini peanut butter cups.
6) Scoop rounded tablespoonfuls of dough onto the prepared baking sheets; a tablespoon cookie scoop works well here. Flatten each cookie to about 1/2" thick.
7) Bake the cookies for 7 to 9 minutes, or until they're set and you can smell chocolate. Remove them from the oven, and cool on a rack.
Yield: about 3 dozen cookies.