Preheat oven to 350°F. Prepare mini muffin pans by spraying lightly with cooking oil.

In a small pot, mix the butter, water and cocoa powder and bring to a boil. Set aside.

In a large bowl, mix the flour, sugar, baking soda, salt, buttermilk, vanilla and eggs. Add in the chocolate mixture and mix until well combined.

Fill each muffin cup with a heaping teaspoon. Bake 13-15 minutes.

Let cool in pan. Indent each brownie with a spoon or the tip of your finger. Heat the peanut butter and spoon a little into each brownie. Top with peanut butter and chocolate chips.

Let cool completely. Serve.