01 - Preheat the oven to 375°F (190°C).
02 - Cut the tops off the bell peppers and remove the seeds and membranes. Lightly brush the insides with olive oil and set aside.
03 - Heat 1 tablespoon of olive oil in a large skillet over medium heat. Add the onion and sauté for 2–3 minutes until softened. Add the garlic and cook for an additional 1 minute until fragrant.
04 - Add the chopped spinach to the skillet and cook until wilted, about 2 minutes. Remove from heat and let cool slightly.
05 - In a large mixing bowl, combine the cooked chicken, spinach mixture, ricotta cheese, 1/2 cup mozzarella, Parmesan cheese, dried Italian herbs, salt, and black pepper. Mix thoroughly until evenly combined.
06 - Fill each bell pepper evenly with the chicken Florentine mixture, pressing gently to pack the filling.
07 - Arrange the stuffed peppers upright in a baking dish. Spoon a portion of marinara sauce over each pepper, then sprinkle with the remaining mozzarella cheese.
08 - Pour about 1/4 cup of water into the bottom of the baking dish to prevent the peppers from sticking.
09 - Cover the dish loosely with aluminum foil and bake for 25 minutes.
10 - Remove the foil and continue baking for 10 minutes until the cheese is golden and bubbly and the peppers are tender. Let cool slightly before serving.