Pre-heat oven to 375°F.
Sprinkle salt and pepper over the chicken breasts
Melt 1 to 2 tablespoons butter in a large skillet over medium-high heat.
Add half of the chicken, and cook 5 minutes, or until browned, turn and cook for another 3 minutes.
Transfer to a plate (chicken will not be cooked completely at this point).
Repeat procedure with 1 tablespoon butter and remaining chicken. Wipe the skillet clean.
Melt 2 tablespoons butter in skillet over medium-high heat.
Add shallots, and saute 3 minutes or until translucent.
Add garlic, and saute for 1 minute.
Add mushrooms and cook, stirring, 8 minutes, or until tender.
Stir in sherry and cook, stirring often, 2 minutes.
Melt remaining 3 tbsp butter in a different large saucepan over medium-high heat.
Whisk in flour; cook, whisking constantly, about 2 minutes.
Gradually whisk in stock and bring to a boil. Cook and whisk until slightly thickened, about 3 minutes.
Remove from heat and add rice (reserve the flavor packet for another use) and the cheese, parsley, sage, salt, pepper, and shallot/mushroom mixture.
Lightly grease a 13/9-inch baking dish with cooking spray.
Spoon mixture into dish and then top with chicken.
Bake for 45 minutes, or until chicken reaches 165 F on an meat thermometer.
Remove from oven, and let stand 10 minutes.
Sprinkle with almonds and sage.