Heat a frying pan and sweat the chopped onions in olive oil until soft.
Blanch the herbs in boiling water, drain, and squeeze out excess moisture.
Purée the herbs, onions, black pepper, and roasted peppers in a food processor.
Preheat the oven to 190°C.
Remove the bone from the monkfish tails while leaving 5cm attached at the end.
Season the fish and spread the herb-pepper mix inside the tails.
Close the fish tails to sandwich the filling inside.
Wrap each tail tightly in four slices of prosciutto and chill for one hour.
Sear the wrapped fish in a hot frying pan with olive oil until browned on all sides.
Roast in the oven for 15 minutes and serve.