1
Cut the end of the stalks off the brussels sprouts. Remove any dried or damaged outer leaves. Wash the sprouts with water and drain. Place them in boiling salted water and cook over a high heat for 15 to 20 minutes. When they are cooked through, you should be able to insert a knife easily into them. Drain and keep warm.
2
While the sprouts are cooking, peel and chop the onion.
3
For the mustard sauce:
Pour the cream into a bowl and mix in the mustard, cornstarch and pepper.
4
Heat the butter in a frying pan and add the onions. Cook over a medium heat until they turn brown.
5
Pour the brussels sprouts over the onions. Add the mustard sauce and mix thoroughly. Season with salt and pepper to taste.