Annabel Karmel's ratatouille omelette

Ingredients

• 1 ½ tbsp olive oil
• 1 small onion, sliced
• Half aubergine, sliced
• 1 small courgette, sliced
• Half red pepper, deseeded and diced
• 1 small clove garlic, crushed
• 1 x 200g tin chopped tomatoes
• 2 tbsp basil, chopped
• A knob of butter
• 4 British Lion eggs
• 3 tbsp milk
• 1 tomato deseeded and diced
• 30g parmesan, grated
• 30g gruyere cheese, grated