Heat oven to 190C/170C fan/gas 5. Cook the macaroni following pack instructions, then drain in a colander. Meanwhile, melt the butter in a large saucepan over a medium heat. Once melted, add the shallots and cook very gently for 10-15 mins until soft. Add the flour, mix well, then slowly add the milk, a splash at a time, mixing well after each addition to make a smooth sauce. Once all the milk has been added, keep cooking and stirring until the sauce thickens. Stir in the mustard, cream cheese, cheddar and egg. Season well.