Heat oven to 350 degrees.
Mash bananas in a medium sized bowl and set aside.
Beat together butter and sugars. Beat in egg.
Sift together flour and baking powder. Add to butter/sugars/egg mixture. Beat well.
Fold in mashed bananas and sliced strawberries.
Grease 12 muffin tins or use paper liners. Fill tins right to the top with batter.
Bake at 350 degrees for 25 minutes or until toothpick inserted in a muffins comes out clean
12 Large Muffins