Wash the fish filets well. If you use frozen fish, thaw the filets before washing. Put them into a plate and marinate them with the lemon juice for at least 10 minutes. Meanwhile you can prepare the parsley crust. Wash the parsley and chop the leaves finely. Mix the bread crumbs with the smashed garlic cloves, the butter, the egg white, one tea spoon of salt and plenty of black pepper to obtain a smooth paste. Cover the bottom of an oven proof dish with the olive oil and place the fish filets inside. Cover the filets with the parsley crust and bake 20 minutes in the oven at lowest temperature. After this place the dish under the grill until the crust is golden brown and really crunchy. Serve with vegetables or a salad and garlic bread or toast.