Heat 2 tablespoons of butter over medium heat in a large pan. Season the chicken breasts to taste with salt and pepper.
Add the chicken to the pan and cook for 4-5 minutes on each side, or until golden brown and cooked through.
Remove the chicken from the pan and cover with foil to keep warm. Add the mushrooms to the pan.
Cook the mushrooms for 4-5 minutes or until tender. Remove the mushrooms from the pan. Wipe the pan clean with a paper towel.
Add 1 tablespoon of butter and the garlic to the pan and cook for 30 seconds. Stir in the flour and cook for 1 minute more.
Add the wine to the pan and bring to a simmer.
Cook for 2-3 minutes or until wine is reduced by half.
Stir in the cream and cook for another 3-4 minutes until the sauce has reduced by about half and has started to thicken. Stir in the parmesan cheese. Season the sauce with salt and pepper.
Add the spinach to the pan. Simmer for 2-3 minutes or until spinach has wilted. Stir the mushrooms into the sauce.
Place the chicken breasts back into the pan and spoon the sauce over the top of the chicken. Sprinkle with parsley, then serve.