Method

​1 Preheat the oven to 180°C/fan 160°C/gas mark 4. Grease the inside of your ovenproof dish.

2 Peel the onion and cut it finely. Peel the potatoes and dice them into cubes. Heat the oil in a frying pan over a medium heat, add the onion and potatoes and cook for about 4 minutes until they begin to soften.

3 While the potatoes and the onion are cooking, peel and crush the garlic and slice the mushrooms. Add them to the frying pan and cook for a few minutes more, until the onion and potatoes begin to brown.

4 Take the frying pan off the heat. Spoon the onion and potato into the bottom of the dish spreading it out evenly. Add the peas and sweetcorn too.

5 Break the eggs into a small bowl. Beat them with a fork, then stir in the milk and a little salt and black pepper to season. Pour the beaten egg over the vegetables in the dish. Slice the tomatoes and place on the top along with the grated cheese. Bake the omelette in the oven for 45 minutes until it has set.

6 Run a knife around the edge of the dish to loosen the omelette, then cut it into quarters. Use a spatula or fish slice to serve it up.