Cook the macaroni in a large saucepan of salted boiling water according to the packet instructions until al dente, then drain and put in a warmed serving bowl. Cover and keep warm.
Gently heat the mascarpone, Cheddar, milk and mustard in a saucepan until melted into a sauce. Stir in the ham and cook gently for 1–2 minutes. Season to taste with salt and pepper.
Serve the macaroni with the cheese sauce spooned over, garnished with chopped parsley.