1. Place 1 paper cupcake liner in each of 12 glass 6-ounce custard cups; set aside.
2. In small bowl, combine flours, sugar, salt and baking powder; set aside.
3. In large mixing bowl, combine cereal, bananas and milk. Let stand 2 minutes or until cereal has softened. Add egg, oil and peanut butter, beating until smooth. Add flour mixture, stirring only until combined. Place 1/4 cup batter in each paper-lined custard cup. Arrange 6 cups on large microwavable plate in center of microwave.
4. Cook on HIGH 1 minute and 30 seconds. Rotate the plate 1/4 turn and cook on HIGH 1 minute and 30 seconds longer. With hot pads, carefully remove muffins from microwave and place on wire rack. Repeat with remaining muffins. Let stand on wire rack 5 minutes before serving.