- Preheat oven to 220°C/200°C fan/gas mark 7.
- Mash together the cooked potatoes with the other cooked vegetable(s).
- Beat the cream, egg yolks, grated cheese, and salt and pepper into the vegetable mixture.
- Whisk the egg whites until stiff, then fold them lightly but evenly into the vegetable mixture.
- Spoon the mixture into a greased 18cm/7 inch soufflé dish.
- Bake for 20 minutes until the soufflé has risen well and is lightly browned on top.
- Serve immediately with a mixed salad.