Marinate the rabbit in the red wine with all the other marinade ingredients for 3 or 4 hours.
Remove the pieces of rabbit to a colander and let them drain. Pat them dry with kitchen paper. Heat 2 tablespoons of olive oil in a wide casserole together with 20g of butter. When the butter starts to colour, fry the pieces of rabbit until they are a glossy, mahogany brown, then transfer them to a plate.
Turn down the heat a bit and brown the onions. Add a tablespoon or more of the flour, according to how thick you want the gravy – I do not like it too thick, and prefer to use less flour. Stir the flour together with the juices in the casserole until brown, then add a cupful of the marinade. Stir it well and then add the rest. Season with salt and pepper.
Add a cube of sugar and the stock, bring to simmering point, return the pieces of rabbit and simmer gently for 25–30 minutes for a tame rabbit, 1–1½ hours for a wild one, until the meat is tender. Turn the pieces of rabbit occasionally and add more liquid if needed.
Remove the pieces of rabbit to a deep dish. Cover with foil and keep warm. If necessary, reduce the sauce until it reaches a velvet consistency. Strain it and return it to the casserole.
Heat the remaining oil and butter in a frying-pan, together with the crushed clove of garlic. Fry the mushrooms briefly and add them, together with the pieces of rabbit, to the sauce. Fry the rabbit liver, slice it and add it to the casserole. Heat through and serve with baked potatoes and a green salad.