Remove the half-cooked vegetables from the oven, remove the foil and put them back in the oven on the grill so that the potatoes are browned. Then take it out, put it on top of the mushrooms and sprinkle with cheese mixed with garlic. Return to the oven and bake until the cheese is completely melted.While the gratin is languishing in the oven, cook the rabbit, or rather, its legs. The leg is best taken from the front, but the back is also good.
Wash, dry with paper towels and fry in a slow cooker on the "Frying on both sides" program. Sprinkle with mustard and spices, add white wine and simmer on the "Stewing" program until ready. It usually takes about 20 minutes, but it all depends on your slow cooker.
If everything is done quickly, the casserole will be ready almost simultaneously with the rabbit!