- Preheat the oven to 200°C/gas 6 and put a baking sheet in the oven to heat. Lightly oil the inside of a 1.25 litre soufflé dish. Sprinkle with the breadcrumbs, then tilt the dish and tap around the edge to distribute them evenly.
- Melt the butter in a saucepan over a moderate heat. Sprinkle in the flour, then cook for 1 minute, stirring all the time. Slowly add in the milk, whisking constantly, until the sauce comes to the boil and thickens. Simmer for 2 minutes, stirring occasionally, then season with nutmeg and salt and pepper to taste.
- Remove the sauce from the heat and cool slightly, then beat in the egg yolks, one at a time. Add the goat's cheese, half the Parmesan and the mustard and beat well to mix. Return the pan to the heat and reheat gently, just until the cheese has melted to make a thick, smooth sauce. Set aside to cool. Meanwhile, gently heat the ratatouille in a separate pan or in a dish in the microwave.
- Whisk the egg whites in a large, clean bowl until stiff peaks form. Whisk one third of the egg whites into the soufflé mixture to lighten, then use a large metal spoon to fold in the remaining whites.
- Spoon the hot ratatouille into the bottom of the soufflé dish. Spoon the cheese mixture on top and sprinkle with the remaining Parmesan. Place on the preheated baking sheet and bake for 20–25 minutes until well risen and golden. Serve at once.
Parmesan cheese is not truly vegetarian, as it contains animal rennet. To make this dish 100% vegetarian, omit the cheese or find a suitable vegetarian substitute made without animal rennet. In supermarkets look for the 'parmesan style hard cheeses' which are suitable for vegetarians.
For a spinach and cheese soufflé, omit the ratatouille. Put 450g rinsed young spinach leaves in a saucepan over a moderate heat, with just the water clinging to the leaves, and cook for 2 minutes until they wilt and turn dark green. Squeeze out all excess water and season to taste. Beat into the sauce in step 3, before adding the cheese.
You will know the egg whites are stiff enough when you can turn the bowl upside-down without them falling out.