Preheat oven to 375°F and season chicken with salt and pepper.

Sear chicken in an oven-safe skillet with olive oil until golden. Remove and set aside.

Sauté onion and mushrooms until softened and golden. Add garlic and cook briefly.

Stir in spinach, cream, broth, and thyme. Simmer until slightly thickened.

Return chicken to pan, top with mozzarella and Parmesan.

Bake uncovered for 20–25 minutes until chicken is cooked through and cheese is melted.