Preheat the oven to 180 ℃/170℃ fan/gas mark 4. Place the meat on a plate and sprinkle with the flour and season with salt and pepper. Toss the meat in the flour to coat.
Melt the butter with the oil in a frying pan and add the bacon. Cook until browned on all sides. Transfer to an ovenproof casserole dish using a slotted spoon.
Add the onions to the pan and cook gently until softened and beginning to colour, then add to the casserole dish.
Brown the meat on all sides and transfer to the casserole dish.
Sprinkle any remaining flour into the pan. Add the sugar, ale and stock, stirring well to scrape up any juices that are sticking to the base of the pan. Bring to the boil then pour into the casserole dish.
Stir to combine the ingredients, and add the bouquet garni. Cover and cook for 1 ½ hours or until the meat is tender.
Remove the bouquet garni, taste and adjust the seasoning as required. Spread the french bread slices with a generous layer of mustard and place in a ring on top of the casserole. Cook uncovered for a further 15–20 minutes.
Notes
Freeze the carbonnade after cooking until tender and allowing to cool. Add the bread garnish when reheating. Freeze for up to 6 months.