Pre-heat oven to 200°C, 180°C fan, 350°F, Gas Mark 4.
Cook the pasta in a large saucepan of boiling, salted water for 7 minutes, until almost cooked. Pour into a colander, refresh under cool water and drain again.
Put the bacon lardons in a large frying pan and place over a medium heat. Cook for a few minutes, stirring occasionally until pale golden. Add the sliced chicken to the pan with the rosemary and continue to cook for 5 minutes. Add the peas and garlic for the final minute. Turn off the heat and stir in the crème fraîche and milk to form a smooth sauce. Stir in the pasta and season with salt and pepper.
Transfer to a ceramic baking dish and scatter with the parmesan. Bake for 20 minutes, or until golden and bubbling. Serve with a rocket salad.
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