#### **Preparation:**
1. Preheat the oven to 180°C (gas mark 6).
2. Lightly butter a large baking dish.
3. In a bowl, beat the eggs with the milk. Season with salt and pepper.
4. Add the peppers, onion, and ham (if using) to the egg mixture.
5. Pour everything into the prepared dish. 6. Sprinkle grated cheese generously on top.
7. Bake for about 30 to 35 minutes, or until the top is golden brown and the gratin is firm in the center.
8. Let cool for a few minutes before cutting into squares and serving.
