Prep the peppers: Preheat your oven to 400°F (200°C). Slice the bell peppers in half lengthwise and remove seeds and membranes.
Drizzle with olive oil, season with salt and pepper, and place cut-side up in a baking dish. Roast for 12–15 minutes until slightly tender but still holding shape.
Make the Alfredo base: While the peppers roast, melt the butter in a skillet over medium heat. Add garlic and cook 30–60 seconds until fragrant, not browned.
Add cream and cream cheese: Pour in the heavy cream and whisk in the cream cheese until smooth and slightly thickened, 2–3 minutes.
Keep the heat gentle to prevent breaking.
Stir in cheese and seasoning: Add Parmesan, nutmeg, Italian seasoning, and a pinch of salt and pepper. Whisk until the sauce is velvety and coats the back of a spoon. If too thick, splash in a little more cream or water.
Fold in chicken: Add the cooked chicken to the sauce and stir to combine.
Let it warm through for 1–2 minutes. Taste and adjust seasoning.
Stuff the peppers: Spoon the creamy chicken mixture into each roasted pepper half. Don’t overfill—aim for level and tidy mounds.
Top and bake: Sprinkle with extra Parmesan and the mozzarella.
Return the dish to the oven and bake for 10–12 minutes, until the cheese is melted and lightly golden.
Finish and serve: Let the peppers rest for 5 minutes so the filling sets. Garnish with chopped parsley or chives. Serve warm.