Preheat the oven to 350 degrees. Arrange the bread slices on a baking sheet; brush with the oil. Bake until crisp, 10 minutes. Rub with the garlic and tear into 1-inch pieces.

In a saucepan, heat 3 tablespoons of the oil. Add the saffron and all but 1/2 cup of the leeks. Cook over moderate heat until tender, 4 minutes. Add the 1/2 cup of red wine; reduce over high heat to 2 tablespoons. Add the stock; simmer for 3 minutes. Stir in the toasts and simmer 3 minutes.

Working in batches, puree the soup in a blender. Return the soup to the saucepan. Stir in the cream and the remaining 1 tablespoon of red wine, season with salt and pepper, and keep warm.

In a nonstick skillet, heat the remaining 1/2 tablespoon of oil. Add the reserved leeks and cook over moderate heat until softened, 3 minutes. Using a heatproof spatula, form the leeks into four 2-inch rounds. Sprinkle 1 tablespoon of the cheese over each round. Cook over moderate heat until melted, about 3 minutes. Transfer the rounds to a plate and let cool until crisp.

Ladle the soup into bowls, top with the leek crisps, and serve.