1/2 tsp of mustard powder, or a tsp of Dijon mustard
Peel Onion, and cut into 4 pieces. Place in a saucepan with the milk and a pinch of salt and pepper, and bring to the boil. Turn off the heat, cover and leave for an hour, then strain through a colander, and reserve the milk.
Tip Macaroni into a large pan of boiling salted water, and simmer for 10 mins. Drain in a colander and refresh with cold water
Melt butter in a small pan, and gently fry lardons of Smoked Bacon for about 3 minutes until beginning to brown, then remove from plan with a slotted spoon, and set aside in a bowl.
Tip flour into butter and bacon fat, and combine to form a roux. Add the reserved milk a bit at a time, whisking between additions to keep the sauce smooth. Bring to the boil and simmer for 5 minutes.
Cut slices of bread into soldiers, and wizz in a food processor until coarse crumbs are formed, then stir in a handful of grated cheese.
Add the remaining grated cheese to the white sauce, along with the mustard powder or mustard and stir in well.
Combine the cooked Macaroni, the bacon and the cheese sauce and stir together well. Place mixture in a large greased ovenproof dish.
Top with the breadcrumb and grated cheese mix, and bake in the oven at 180 degrees C (160 degrees C fan oven) for 45 minutes. Serve immediately with salad or peas, and allow yourself some ketchup if you like it!