Season the chicken breasts with salt, pepper, and thyme (if using).
Heat olive oil in a large skillet over medium-high heat.
Add the chicken breasts to the skillet and cook for 6-7 minutes on each side until golden brown and cooked through.
Remove the chicken from the skillet and let it rest on a plate.
In the same skillet, add minced garlic and sauté for about 1 minute until fragrant.
Pour in the heavy cream and bring it to a gentle simmer.
Stir in the grated Parmesan cheese until melted and well combined.
Add the fresh spinach and allow it to wilt in the sauce for about 2 minutes.
Slice the rested chicken and return it to the skillet, coating in the creamy sauce.
Serve warm, optionally garnished with extra Parmesan and pepper.