Peel the potatoes. Put a large pan of water on the boil. Add a small sprinkle of sea salt. Gently put the potatoes in and boil until tender. Drain and allow to steam and dry out for a moment. Add in the butter and milk, seasoning and cheese and stir in. Set aside.

Preheat the oven to 180℃ fan, 200℃, gas 6

Ask your fishmonger to pin bone and skin your fish. You can poach it in whole fillets or large bitesize chunks.

Place the milk in a large saucepan. Gently sit in the fish, fish stock pot, bay leaf and dill if using. Turn on low to medium heat and allow to poach for 5-6 minutes.

When cooked, remove the fish and set aside. Save the milk, this will be used for the creamy sauce.

Melt the butter in a pan, stir in the flour, and whisk this over low heat for 1 minute, until it goes dry and sandy.

At this stage, gradually start to whisk in the milk that you used to poach the fish, little by little until it is fully combined and forms a thick sauce.

Take it off the heat, stir in the mustard and sour cream, then sprinkle in the grated cheddar, season with salt and pepper.

Set aside.

Place the flaked fish and layer it in the bottom of an oven-proof dish. Mix all the varieties around.

Sprinkle in the frozen peas.

Pour over the creamy sauce and combine. Spoon on the mashed potatoes. Spread and smooth it out with a spoon.

Sprinkle on the grated cheddar on top.

Bake in the oven for 35-40 minutes until golden, bubbly and hot all the way through.

Serve with some in-season green vegetables, like leeks, wilted spinach/kale and some peas.

Enjoy.