Ingredients

• 1 leg of lamb (6 to 7 pounds), boned (net weight 3 ½ to 4 pounds)
• 1 teaspoon salt
• ½ teaspoon freshly ground pepper
• a cloves garlic, slivered

ONION PUREE

• 8 tablespoons unsalted butter
• 6 tablespoons raw long-grain white rice
• 3 medium onions, sliced
• ½ teaspoon salt
• ¼ teaspoon freshly ground white pepper

WHITE SAUCE

• 2 tablespoons unsalted butter
• 1 tablespoon unbleached, all-purpose flour
• ¼ cup rich chicken stock, preferably homemade (page 317)
• 1 tablespoon fresh lemon juice
• ½ cup heavy cream
• 2 egg yolks, slightly beaten
• 1 cup rich chicken stock
• 3 to 4 tablespoons unsalted butter
• ¼ cup dry bread crumbs
• ¼ cup chopped fresh parsley
• ¼ cup melted butter

Instructions

1. Preheat oven to 350°. Trim the fat from the lamb and rub the meat with the salt and pepper. Pierce the lamb at regular intervals with the tip of a small knife, and insert the garlic slivers. Place the lamb in a roasting pan, and roast the lamb 50 to 60 minutes (a meat thermometer will register 140° for rare, 145° for medium-rare and 165° for well done).
2. To prepare the onion purée: Melt the 8 tablespoons of butter in a saucepan and stir in the rice, onions, salt and pepper. Cook the mixture, covered, over medium heat for 25 minutes. Purée the sauce, using a food processor fitted with the steel blade or a blender. Set the purée aside.
3. To prepare the white sauce: Melt the 2 tablespoons of butter in a saucepan, whisk in the flour, cook this roux until it bubbles thoroughly. Whisk in the chicken stock and lemon juice. Combine the cream with the beaten egg yolks and slowly pour this into the sauce while whisking vigorously. Add the onion purée, adjust the seasoning and remove it from the heat.
4. Remove the roast from the oven and increase the oven temperature to 4oo°. Let the meat stand 15 to 20 minutes, then slice it into serving portions.
   Spread some sauce over each slice, and arrange them, overlapping, in an ovenproof serving dish.
5. Add the 1 cup of chicken stock to the roasting pan, and deglaze the pan over high heat, stirring to bring up the browned bits. (If preparing the dish in advance, set these juices aside and reheat just before serving time.) Swirl in the 3 to 4 tablespoons of butter.
6. Sprinkle the bread crumbs and parsley over the sliced meat, then drizzle on the pan juices and butter. Reheat the meat in the 400° oven for 15 minutes, and serve.

Note:

This dish may be cooked ahead and refrigerated, covered. Bring in to room temperature before reheating.

Source: Page 248 of The George and Piret Munger Cookbook