Place a pheasant or chicken breast, boned side up, between 2 pieces of plastic wrap. Working from the center to edges, very gently pound with the flat side of a meat mallet till 18 inch thick. Remove plastic wrap. Repeat with remaining pheasant or chicken.
In a shallow dish, stir together flour, salt and pepper. Lightly coat pheasant or chicken on both sides with flour mixture; shake off excess.
In a large skillet, melt 2 tablespoons of the butter. Cook pheasant or chicken, half at a time, over medium heat for 3 to 4 minutes till no longer pink, turning occasionally. Remove from skillet and keep warm.
In the same skillet, add the remaining 1 tablespoon butter. Cook mushrooms, shallots and celery in hot butter for 5 to 6 minutes or till tender, stirring often. Carefully add the cream sherry or chicken broth, lemon peel and juice. Using a wooden spoon, stir and scrape up browned bits in skillet.
Add the 12 cup chicken broth. Bring to boiling; reduce heat. Cook, uncovered, over medium-high heat for 6 to 8 minutes or till most of the liquid has evaporated (measures about 2 tablespoons), stirring often. Whisk in the whipping cream and sour cream. Cook, whisking constantly, over medium heat for 5 minutes or till mixture thickens and is reduced to about 1 cup. Return pheasant or chicken pieces to skillet; heat through.
In a 12-inch skillet melt the 2 tablespoons butter. Add garlic. Cook garlic for 1 minute. Add the spinach. Using two spoons or tongs, toss 30 seconds or till spinach is coated and just wilted.
To serve, evenly divide spinach among 4 warmed dinner plates. Place a pheasant or chicken piece on each bed of spinach; pour sauce over it. Sprinkle with almonds.