White Fish Golden Gratin

Preheat the oven to 190°C | 375F | gas mark 5.

Heat the oil in a frying pan and cook off the onion until it softens and starts to brown. Remove from heat.

In a saucepan place the fish and milk, salt and pepper and bring to the boil, mix in the onions, turn the heat down, cover and simmer for 5 minutes. Take the pan off the heat and leave to stand for a further 5 minutes.

Meanwhile rub the flour, butter, chopped herbs and Parmesan cheese together in a mixing bowl until it makes fine crumbs. Remove the fish from the pan, keeping the milk and onions.

Mix the cornflour into a smooth paste with a little water. Stir into the milk with the gruyere cheese and return to the heat and bring to the boil whilst stirring until the sauce starts to thicken.

Stir in the fish add some salt and pepper and stir for a further 1 minute until the sauce is nice and thick.

Pour the mixture into a shallow oven proof chef's pan or ovenproof dish. Spread the crumble mixture over the top and bake in the oven for 35-40 minutes until crumble is golden brown.