Preheat the oven to 200°C. Beat the eggs with salt, pepper and mace in a medium bowl. Stir in the crab. Defrost the peas in boiling water and drain. Chop the spring onions and add both to the bowl. Stir in the cream, sherry and half the cheese.
Use the mixture to fill the flan case and place, in its foil container, on a heavy baking tray. Sprinkle the rest of the cheese on top and bake high in the oven for 20 minutes.