Classic Fish Pie with Creamy Sauce and Cheesy Herb Crust

Ingredients

• 2 cod fillets (250g)
• cooked prawns (100g)
• 1 white onion
• 1 leek
• a knob of butter
• milk
• salt
• pepper
• 50g butter
• 50g plain flour
• The milk used for the filling (see method)
• approx 8 potatoes peeled and chopped
• a dash of milk from the filling (see method)
• a few slices of white bread
• a handful of herbs (basil,parsley)
• 50g of grated parmesan cheese.
• 50g grated mature chedder cheese