01 - Preheat your oven to 400°F (200°C). Lightly grease a baking dish to prevent sticking.
02 - In a medium bowl, combine the ricotta cheese, finely chopped spinach, grated Parmesan cheese, minced garlic, nutmeg, salt, black pepper, and lemon zest. Mix thoroughly until all ingredients are well incorporated.
03 - Place the chicken thighs on a clean cutting board. Pat them dry with paper towels and season both sides with olive oil, salt, pepper, and dried Italian herbs.
04 - Lay each chicken thigh flat, with the smooth side facing down. Spoon a generous portion of the ricotta-spinach mixture into the center of each thigh.
05 - Carefully roll up each chicken thigh to enclose the filling. Place the rolled thighs seam-side down in the prepared baking dish.
06 - If desired, evenly sprinkle the shredded mozzarella cheese over the top of the stuffed chicken thighs.
07 - Bake for 30–35 minutes, or until the chicken is thoroughly cooked through (reaching an internal temperature of 165°F/74°C) and the tops are golden brown.
08 - Allow the stuffed chicken thighs to rest for 5 minutes before serving to ensure juiciness.