Cut "pockets into your chicken breasts with a sharp knife. (see video or process shots) Keep aside.
For the Filling:
If you use fresh spinach: Prep your fresh spinach. Rinse and pick out withered leaves. Keep a small pot with water to boil and place spinach leaves in to blanch (aka cook briefly) for 3 minutes. Take out from the water and place into a prepared bowl with ice water.
If you use frozen spinach, just thaw it and remove excess waters.
Combine filling ingredients in a bowl, the cream cheese, chopped garlic, chopped spinach, grated cheese of your choice, salt, black pepper, and thyme.
For the Chicken in the Dish:
Preheat oven to 400° Fahrenheit/ 200° Celsius.
Place boneless chicken breasts into your casserole dish next to each other. Sprinkle salt and black pepper over your chicken breasts.
Stuff each chicken "pocket" with the cream cheese spinach stuffing until nothing is left.
For the Sauce:
Pour cream into the sides of the casserole dish.
Sprinkle olive oil over chicken.
Cover chicken dish with aluminum foil and bake for 25 minutes at 400° Fahrenheit/ 200° Celsius.
Take your dish out of the oven halfway through the cooking process and remove the aluminum foil.
Bake the dish uncovered for another 20 - 25 minutes approximately and increase the temperature to 430° Fahrenheit/ 220° Celsius or bake until the chicken is cooked through but juicy moist.
Serve up hot with a side of your choice.
Use fresh or frozen spinach. I prefer fresh baby spinach or regular spinach leaves if possible vs frozen spinach. If I'm late, I will use frozen thawed spinach too.
Pick a cheese of your choice. I like to use grated mozzarella or gruyere cheese.
You can use light or heavy cream, whichever you prefer. Light cream is called table cream too. If you have half and half in your fridge, you can use that too but it has fewer fats and the sauce will turn out more watery.