Preheat oven to 350 degrees F/180 degrees C and grease a 16 cup muffin pan or place 16 paper muffin cup liners in muffin pan.
In a large bowl, combine the flour, sugar, baking powder, baking soda and salt.
In another bowl, whisk the egg, oil, sour cream (or plain yogurt can be used) and vanilla. Stir into dry ingredients just until moistened. Fold in bananas, chopped strawberries and chocolate chips.
Fill greased or paper-lined muffin cups two-thirds full. Bake in preheated oven for 22-25 minutes or until a toothpick inserted near the center comes out clean (toothpick inserted into center of muffin may be a bit moist and gooey because of using fresh chopped strawberries, but that's alright). Cool for 5 minutes before removing from pans to wire racks to cool completely.