Melt butter (2 tablespoons) in a large skillet over medium heat. Add garlic (1 tablespoon) and cook until fragrant, for about 1 minute. Stir in the mushrooms (8 ounces), 1/2 teaspoon salt, 1/2 teaspoon black pepper, and Italian Seasoning (2 teaspoons) continue to cook until tender, about 5 minutes. Remove to a plate and set aside.
Pat chicken breast (4) dry with paper towels to remove any moisture. Mix together flour (2 tablespoons), and 2 tablespoons Parmesan cheese in a shallow bowl or plate. Dredge chicken breasts in flour mixture, shaking off excess.
Add (2 tablespoons) olive oil to the skillet. Cook the chicken over medium heat, until the chicken is cooked. Remove the chicken to a plate and loosely cover it with aluminum foil to keep it warm.
Add the chicken broth (1/2 cup) to the pan and bring to a boil over medium heat, stirring well to loosen all the brown bits on the bottom of the pan. Reduce the heat and simmer uncovered, until the broth is reduced to about 1/4 of a cup.
Stir in heavy cream (1 1/2 cups) and 1/2 cup Parmesan cheese and cook over medium heat until sauce begins to thicken. Stir in spinach (1 cup). Add mushrooms and chicken back into the sauce and flip it over once to coat. Serve.