Preheat oven to 180 C (350 F) and brush a muffin tray with olive oil or butter.
Mash banana and add milk and egg, whisking until well combined.
Slowly add flour while mixing until well combined.
Spoon small amounts into the muffin tray cavities, enough to make a layer almost a cm thick.
Put 3 berries in each one.
Bake for 12 mins, or until a toothpick inserted into them comes out clean.