Prep the peppers: Preheat your oven to 400°F (200°C). Slice the tops off the bell peppers and remove seeds and membranes. Drizzle with olive oil, season with a pinch of salt and pepper, and place cut-side up in a baking dish.

Pre-bake the peppers: Bake for 10–12 minutes to soften slightly. This helps them cook through without becoming mushy later.

Make the Alfredo sauce: In a large skillet over medium heat, melt the butter. Add the minced garlic and cook 30–60 seconds until fragrant. Pour in the heavy cream and add cream cheese. Whisk until smooth and gently simmer for 2–3 minutes.

Add cheeses and seasonings: Stir in Parmesan, Italian seasoning, onion powder, salt, and black pepper. Simmer 2–3 more minutes until thick and creamy. If using red pepper flakes, add them now. Taste and adjust seasoning.

Stir in chicken (and spinach if using): Add the cooked chicken and fold to coat. If adding spinach, stir it in and cook 1–2 minutes until wilted. The filling should be thick and creamy.

Stuff the peppers: Spoon the chicken Alfredo mixture evenly into the pre-baked peppers. Top each with mozzarella and a sprinkle of extra Parmesan.

Bake: Return to the oven and bake 12–15 minutes, until the cheese is melted and lightly golden and the peppers are tender.

Rest and serve: Let the peppers rest for 5 minutes so the filling sets slightly. Garnish with cracked black pepper or chopped parsley if you like. Serve warm.