Step 1

Preheat the oven to 180°C. Brush a 24cm oven-proof pan or round baking dish with oil.

Step 2

Boil the eggs for 8-10 minutes. Drain and rinse under cold water before peeling and slicing into quarters.

Step 3

Melt the butter over a moderate heat in the same saucepan and mix in the flour, cook stirring for 2 minutes before gradually adding the milk, whisking continuously until the mixture bubbles and thickens. Cook it for 10 minutes. Remove from the heat and stir through the mayonnaise.

Step 4

Lay a tortilla in the base of the baking dish and cover with half of the red onion, celery, tuna and sliced egg. Spoon over a third of the sauce, sprinkle with a third of the cheese, half the parsley and season with salt and pepper.

Step 5

Cover with another tortilla and repeat the process.

Step 6

Finish off with a tortilla on top, spread with the sauce and sprinkle with the remaining cheese.

Step 7

Bake for 20 minutes until the top is crisp and golden.