Heat olive oil in a large skillet. Then, add sliced chicken thighs. Cook for a few minutes on each side until nicely browned. Then, season with salt and pepper to taste. Remove browned chicken thighs slices from a skillet. Set aside. Don't turn off the heat.
Add sliced mushrooms to a hot skillet. Cook for a few minutes until lightly browned. Season with salt and pepper to taste. Stir to combine. Then, remove from a skillet. Set aside. Don't turn off the heat.
Prepare the creamy sauce. Melt butter in the same skillet. Then, add minced garlic and cook for 1 minute until fragrant. Add all-purpose flour and stir until combined. Then, add half and half, chicken broth, and grated parmesan cheese to a skillet. Stir to combine. Season with salt and pepper to taste. Stir. Then, add fresh spinach and cook until wilted.
Return browned chicken thighs slices and sliced mushrooms to a skillet. Mix to combine. Cook until warmed. Enjoy!