step 1
Preheat the oven to gas mark 5 / 190C / 375F. Add the egg to the mashed bananas in a large bowl and beat with a fork until incorporated.
step 2
Add the sugars and the melted butter and beat again until combined.
step 3
Stir together dry ingredients and sift into wet. Tip in the bran left in the sieve. Fold the dry ingredients gently into the wet in figure-of-eight movements with a metal spoon.
step 4
Spoon mixture into muffin cases. If nutella is not soft, gently warm in microwave. Add 1/2 tsp to each case and swirl with a cocktail stick.
step 5
Bake for 20 minutes, then insert a knife. If blade comes out clean, they are done. If not, return to oven and keep checking.