Preheat oven to 350°. Spray or grease 12 muffin cups.

In a large microwave-safe bowl, combine sugar, butter, and water. Microwave on high for 1 minute or until butter is melted.

Stir in 3/4 cup semi-sweet chocolate chips until melted.

Stir in egg and vanilla extract.

Add flour and baking soda, stirring until blended. Allow to cool to room temperature.

Stir 1/2 cup each peanut butter chips and semi-sweet chocolate chips. Spoon batter by heaping tablespoonfuls into muffin cups.

Bake for 13-15 minutes or until top is set and a toothpick inserted into the center comes out slightly wet. Place pan on wire rack. Centers of brownies will fall upon cooling. If not, tap centers with the back of a teaspoon to make a hole.

Place peanut butter in a small microwave-safe bowl. Microwave on high for 45 seconds, then stir.

While brownies are still hot, spoon about a tablespoon of peanut butter into the center of each brownie. Top with semi-sweet chocolate chips and peanut butter chips. Cool completely in pan.