Pre heat the oven to 200C / 180C fan / gas mark 6 and bake the potatoes in their jackets for about 1 hour until tender in the centre.
Make the white sauce by melting the butter in a saucepan then stir in the flour. Cook for 1 minute then gradually whisk in the milk. Once all the milk is added keep stirring and bring everything to the boil. Simmer for 1 minute then remove from the heat and stir in the cheese and parsley, then season with salt and pepper. Cover the surface with cling film to prevent a skin from forming.
When the potatoes are cooked cut in half then scoop out the centres and roughly mash, setting the skins to one side on a baking tray.
Add ½ of the white sauce to the mashed potato and mix. Spoon the potato mix back into the potato skins. Cover the top of each potato with a strip of sole, season then place back in the oven for 10 minutes or until the fish is cooked.
Mix together the remaining white sauce and prawns and loosen if necessary with a little more milk.
Remove the potatoes from the oven, pour over a little of the prawn sauce and scatter with the remaining parsley.
4 large fluffy potatoes such as Maris Piper or King Edward
40g unsalted butter
30g plain flour
350ml semi – skimmed milk
40g Full fat hard cheese grated e.g. Cheddar
1 tbsp parsley, chopped, plus a little extra for garnish
100g small prawns
4 small fillets of sole, cut in half length ways