In a large saucepan of boiling salted water, cook broccoli about 5 minutes, or until tender; drain. Butter a 9 x 13 x 2-inch baking dish; arrange broccoli across the bottom. Top with turkey; cover with foil to keep warm.
In a large skillet, melt butter over medium heat. Sauté onions and mushrooms until golden brown (add a little broth if mixture seems dry). Add flour, and cook, stirring, 1 minute. Stir in broth; bring to a boil. Reduce heat to low; simmer 3 to 5 minutes, or until thick. Stir in sherry; cook 1 minute. Add cream and 1/4 cup Parmesan; simmer 1 minute. Season to taste with salt and freshly ground black pepper. Remove from heat.
Meanwhile, arrange a rack 6 inches below the heat source, and preheat the broiler to high. Pour sauce over turkey. Top with the remaining 1/4 cup Parmesan and almonds. Broil for 1 minute, or until the sauce bubbles and the almonds are golden brown.