Preheat your oven to 375°F (190°C).

Using a meat mallet or rolling pin, gently pound the chicken breasts to an even thickness of about 1/2 inch.

In a mixing bowl, combine chopped spinach, softened cream cheese, chopped dried cranberries, shredded mozzarella, minced garlic, salt, black pepper, and thyme if using. Mix until everything is well combined.

Lay the chicken breasts flat on a cutting board. Spoon a generous amount of the spinach mixture in the center of each breast, folding the sides over to encase the filling. Secure with toothpicks or kitchen twine.

Heat the olive oil in a skillet over medium heat. Sear each stuffed chicken breast for about 3-4 minutes on each side, or until golden brown.

Transfer the seared breasts to a baking dish and place them in the preheated oven. Bake for 20-25 minutes, or until the chicken is cooked through and reaches an internal temperature of 165°F (75°C).

Once cooked, remove the toothpicks or twine, let the chicken rest for a few minutes, then slice and serve.