Wipe over the partridges and set aside. Trim and dice the streaky bacon and, reserving half, heat the remainder in a heavy flameproof casserole until the fat runs. Add the partridges and brown all over. Peel the button onions, leaving them whole. Trim the mushrooms, leaving them whole, and reserve any stalks. Draw the casserole off the heat and add the button onions, mushrooms and bouquet garni. Pour over the red wine and
Meanwhile, heat the remaining bacon pieces in a saucepan along with the dripping or vegetable fat. Finely chop the onion and add to the pan. Cook gently until the onion is soft. Add the flour and continue to cook gently until the mixture is a dark brown colour – about 15 minutes. Gradually stir in the remaining stock and bring up to the boil, stirring all the time to make a brown sauce. Add any mushroom trimmings, lower the heat and allow to simmer for 30 minutes. If the sauce thickens during cooking time leave it until the partridges are cooked and then thin the sauce with a little of the liquid from the casserole.
When the partridges are cooked, strain off the liquid and remove the bouquet garni. Lift the birds from the casserole, cool for a few moments, then cut the birds in half, removing each breast and leg section from the carcass. Replace these in the casserole with the vegetables. Add any liquid necessary to the brown sauce and season with salt and pepper. Strain the sauce over the birds, sprinkle with chopped parsley and keep hot until ready to serve.