Heat oven to 350 F. Lightly grease a 7x11-inch glass baking dish with butter. Using a rolling pin, flatten the chicken breasts between waxed paper to ¼-inch thick. 

In a small skillet, melt 2 teaspoons of butter. Add the onion and sauté until tender, about 3 minutes. Remove the pan from the heat. Stir in the spinach, cheese, almonds and nutmeg until fully incorporated, about 2 minutes. 

Divide the mixture in half and slightly mound each half in the buttered baking dish. 

Place 1 chicken breast over each mound and brush with melted butter. Bake until the chicken is tender and the juices run clear, 30 to 35 minutes. 

To make the mushroom sauce: In a medium saucepan, melt 1 tablespoon butter. Add the mushrooms and sauté until all liquid has evaporated, about 5 minutes. 

In a small bowl, stir together the instant bouillon and water. Stir the bouillon, lemon juice, heavy whipping cream, sherry and white pepper into the mushrooms. 

Bring to a boil over medium-high heat, stirring constantly, until the sauce is reduced to ⅔ cup and is slightly thickened, 7 to 9 minutes. 

Using a wide spatula, place chicken and spinach on dinner plates. Spoon sauce over the chicken and garnish with chopped parsley. Enjoy!