Bring a pan of water to the boil, add the macaroni and boil for 11-13 minutes until tender. Add the broccoli for the last 3 minutes. Drain.
Meanwhile, heat the oil in a large frying pan. Add the onion and cook for 5 minutes until golden. Add the bacon and cook for a further 5 minutes.
Stir in the flour, then add the soft cheese, milk, sweetcorn and the drained cooked macaroni and broccoli. Cook gently for 2-3 minutes. Season with freshly ground black pepper and transfer to a 1-litre ovenproof dish.
Preheat the grill to high. In a small bowl, mix together the Cheddar, breadcrumbs and parsley, and sprinkle evenly over the macaroni. Cook under the grill for 5 minutes, until golden and bubbling. Serve with the bistro salad.