Steam or cook the carrots in boiling, salted water until tender.
Drain and mash, reserving 150 ml of the stock for the sauce, if liked.
Melt the margarine in a pan, stir in the flour and cook for 1 minute.
Gradually stir in the milk and stock, if used.
Bring to the boil.
Simmer for 3 minutes, still stirring.
Remove from the heat and beat in the egg yolk, carrot purée, salt, pepper and mint.
Whisk the egg whites until stiff and fold into the carrot mixture, using a metal spoon.
Turn into the soufflé dish and sprinkle with the cheese.
Stand on a baking tray and bake for 45 minutes, or until well risen and golden brown.
Serve at once.
Alternative Suggestion :
Cook, then purée 100 g whole brown lentils and add to the sauce with 15 ml tablespoons each summer savory
and parsley and a pinch of coriander in place of the carrots and mint.