Peel and chop the onion. Cook the egg in boiling water for about 8 minutes. Clean the broccoli, cook in boiling salted water for about 5 minutes and keep warm. Heat oil in a pan, fry onion cubes and mustard.
Add stock and "finesse", season with salt and pepper and bring to the boil. Stir the starch with a little water until smooth and thicken the sauce with it, bring to the boil again. Wash and chop the parsley.
Heat the prawns in the sauce and add the parsley. Peel the egg and cut into 6 corners. Arrange broccoli, egg and sauce on a plate, garnish with parsley. Amaranth tastes good with it.