Season chicken with salt and black pepper.
Heat olive oil in a large skillet over medium-high heat. Sear chicken on both sides until golden. Remove and set aside.
In the same skillet, melt butter. Add mushrooms and cook until browned and moisture has evaporated.
Stir in garlic and cook 30 seconds until fragrant.
Pour in chicken broth and cream, scraping up any browned bits.
Stir in Parmesan and simmer until slightly thickened.
Return chicken to the skillet and simmer until cooked through.
Add spinach and cook until just wilted.
Taste, adjust seasoning, and serve hot.