Preheat oven to 375°F (190°C).
Season chicken breasts with salt and pepper on both sides.
In a large skillet, heat olive oil over medium-high heat. Sear the chicken breasts until golden brown on both sides, about 2-3 minutes per side.
Transfer chicken breasts to a baking dish and bake in the preheated oven for 20-25 minutes or until cooked through.
While the chicken is cooking, add mushrooms to the same skillet and sauté until they are softened, about 3-4 minutes.
Add fresh spinach to the skillet and sauté for another 1-2 minutes or until wilted.
Pour chicken broth into the skillet and let it simmer until reduced by half, about 2-3 minutes.
Add heavy cream, Parmesan cheese, garlic powder, and onion powder. Stir until well combined.
Let the sauce simmer for 2-3 minutes or until thickened.
Serve the chicken breasts with the mushroom spinach sauce and cauliflower rice.