Fish pie

1) Boil the potatoes and mash with 50g of the butter and 200ml of the whole milk. Allow to cool.
2) Make a rue with the flour, butter and the rest of the milk and soya milk. (To make a rue, melt the butter over a low heat, stir in the flour and cook for a couple of minutes. Turn the heat up to medium and add the milk slowly whisking all of the time. It will be very lumpy to begin with but keep whisking and you should have a smooth creamy sauce).
3) Cut the fish into bite sized pieces and add to an ovenproof dish with the can of crab meat.
4) Pour over the rue sauce and turn gently to coat.