Rinse cooled meat, rub dry, rub heartily with a mixture of pepper, juice of one lemon, salt and zest and coat with mustard. Fry heartily on all sides in hot fat for 5 min.
Add onion, garlic and greens. Fry for 5 min.
Gradually pour in hot soup. Roast in 200 °C hot stove for about 90 min. In between, repeatedly baste with roast stock.
When the meat is cooked, cut it into 4 portions and keep warm.
Boil down the meat stock a little, thicken with whipping cream and cornstarch, both stirred smooth with a little cold liquid, and bring to the boil once. Pour a little of it, very hot, over the slices of the roast, and the rest of the sauce separately.
Must always be served very hot.