Halve the duck legs through the joints. Mix the flour with a little seasoning and use to coat the duck pieces.
Melt the butter with the oil in a sturdy roasting pan or flameproof casserole and gently fry the duck pieces for about 10 minutes until browned. Drain to a plate and pour off all but 1 tablespoon of the fat left in the pan.
Add the onions and bacon to the pan and fry gently for 5 minutes. Add the garlic and fry for a further 1 minute. Add the wine, stock and bay leaves and bring to the boil, stirring. Return the duck pieces and cover with a lid or foil. Place in a preheated oven, 160°C (325°F), Gas Mark 3, for 45 minutes.
Add the potatoes to the pan, stirring them into the juices. Sprinkle with salt and return to the oven for 30 minutes.
Add the peas, asparagus and mint to the pan and return to the oven for a further 15 minutes or until all the vegetables are tender. Check the seasoning and serve.