Cut veal into 2-inch squares and sauté until golden in butter with 12 small onions in a thick-bottomed, fire-proof casserole. Sprinkle with flour and add just enough water to cover the meat. Add a bouquet garni and salt and pepper, to taste.
Simmer veal gently for about 1½ hours; cool for a few minutes. Then remove meat pieces and onions to a hot serving bowl or shallow casserole. Keep warm.
Thicken the sauce in the following manner: whisk egg yolks, lemon juice and cream in a bowl. Whisking vigorously, add a ladle of boiling sauce from the veal. Pour this liaison into the sauce and bring it to the boil, whisking well until thick and creamy. Pass sauce through a fine sieve over the meat and onions and serve immediately, accompanied by rice or steamed new potatoes.