Melt the butter in a large pot over medium heat. Add in the shallots, leeks and sauté until soft.

Add in the flour and stir well for one minute.

Then, add the white wine and rub the bottom of the pan with a wooden spoon.

Now add the vegetable stock and bring to a boil.

Follow with the milk and again bring to a boil.

Once boiled add the salmon and cod. Reduce to a simmer.

Add the peas and mussels and simmer for three minutes.

Season with salt, pepper and pour into a large casserole dish. Chill in the fridge.

In a bowl mix the mashed potatoes, egg yolks and grated parmesan. Using a piping bag top the chilled fish stew.

When ready place in a 400F oven for 30 to 40 minutes until hot.

Turn on the broiler, allow the potatoes to brown slightly, and serve.