Chocolate Peanut Butter Muffins

Preheat the oven to 350 degrees F. Line 12 muffin cups with paper liners and set aside. In large bowl, combine 1/2 cup peanut butter and softened butter and beat well until combined. Add brown sugar and sugar and beat until light and fluffy. Add eggs and vanilla and beat well. In sifter or sieve, combine flour, cocoa, baking powder, and baking soda. Sift into peanut butter mixture; add milk, and stir until batter is smooth. Fold in 1 cup chocolate chips. Spoon batter into prepared muffin cups. Bake for 20-25 minutes or until muffins spring back when touched in center. Remove to wire racks to cool. In small bowl combine 1/2 cup chocolate chips with 2 Tbsp. peanut butter; microwave on medium power for 1 minute, then remove and stir until smooth. Frost muffins. Makes 12 muffins