Preheat oven to 375°F. Lightly grease a 9x13-inch baking dish.
Season the chicken breasts with salt, pepper, and paprika on both sides.
In a skillet over medium heat, melt the butter. Add mushrooms and cook until softened, about 5 minutes.
Stir in the garlic and cook for 1 minute. Add the spinach and cook until wilted.
Pour in the heavy cream and let it gently simmer for 3–4 minutes until slightly thickened.
Place the seasoned chicken breasts in the baking dish. Spoon the creamy mushroom and spinach mixture evenly over the top.
Sprinkle mozzarella and Parmesan over the chicken.
Bake uncovered for 30–35 minutes, or until the chicken reaches an internal temperature of 165°F and the top is lightly golden.
Let rest 5 minutes before serving.
