Preheat oven to 220 degrees Celsius. Rinse fish fillets with cold water, pat dry, drizzle with lemon juice and Worcestershire sauce. Grease heat-resistant form with a half of butter. Melt other butter in the pan, pass the flour until creamy, add milk, stir to avoid lumps, add the cream and cook for one minute. Add mustard sauce, salt, pepper and season with nutmeg. Chop dill, add to the sauce. Salt fish fillets, put in shape, season with paprika, pour the sauce, top with flakes of butter and bake in the oven for 15 minutes.