- Start by preparing the white sauce by melting the margarine to which you add the flour. Mix well and pour gradually, without stirring, the hot milk until smooth.
- Season with salt, pepper and nutmeg. Drain the tuna, undo it into chips and drizzle it with a little oil from the tins.
- Grease a pièce and alternate the sauce, the blanched lasagna leaves and the tuna; finish with the sauce well sprinkled with grated cheese and a few pieces of margarine.
- Preheat oven to 250º C and brown until golden brown. Serve with a good salad.