Cut the onions into rings. Mash the garlic clove with a little salt and slowly roast both in hot oil until golden. Dust with flour and pour the hot broth and wine on top and let simmer for a few minutes. Season to taste with salt, pepper and curry.
Toast the white bread slices, place them in ovenproof soup bowls and ladle the soup over them. Grate the cheese and sprinkle on top. Bake in the preheated oven over medium heat for about 10 minutes.