Preheat the oven to 200C/180C Fan/Gas 6. Line 12 muffin holes.
In a large bowl, mash the bananas. Then add the butter, both sugars, caramel and egg (ensure the butter has cooled a little so the egg doesn't cook). Mix with a wooden spoon until combined (avoid electric mixer for the best muffins!).
Add the dry ingredients: flour, baking powder, baking soda and cinnamon Stir until just combined.
Scoop the batter into the lined pan, filling to 2/3rds of the way full.
Add a tsp of caramel to each muffin, swirling a little. Then top with a sprinkle of chopped nuts (optional).
Bake for 20-25 minutes, until the tops are golden brown. Remove from the oven and leave to cool on a wire rack.