1. Beat the peanut butter, brown sugar and 2 tablespoons flour until blended.
2. Melt the chocolate and butter in the microwave and cool.
3. In a large bowl, beat the eggs, sugar and water, then stir in the chocolate mixture and vanilla. Combine baking powder and remaining flour, then gradually add to the chocolate mixture.
4. Fill paper-lined muffin cups 1/4 full. top each with about 1 teaspoon of peanut butter mixture. Spoon remaining batter over the top. Bake at 350 for 13-15 minutes or until centers are set. Cool for 5 minutes before removing from pans. 
5. Ice as you like - I usually add some chocolate icing and sprinkles over the top. 

Serve : 2 dozen cupcakes

Ready in : 15 minutes prep, 15 minutes cooking time