Bring to boil butter, water, and cocoa.
Remove from heat; let cool.
In a bowl mix in with cocoa mixture sugar, soda, flour, buttermilk, salt, vanilla, and eggs.
Preheat oven to 350 degrees F. Spray or grease 40 mini-muffin cups.
Spoon batter evenly into muffin cups, about 1 heaping teaspoon in each.
Bake for 13 to 15 minutes or until top is set and toothpick inserted into center comes out slightly moist.
After brownies are out of the oven, wait for centers to fall. If not, tap the centers with a teaspoon to make an indent for peanut butter.
Over low heat, warm creamy peanut butter.
While brownies are still warm, spoon about half teaspoon warm peanut butter into the center of each brownie; top with chocolate chips and peanut butter chips.
Cool completely in pan. Remove from pan and serve.