Pour cooking oil and sugar into a pot. Brown over strong heat. Add onion and the leek, sliced into thick slices, the white wine, and the stock. Scatter some aniseed, a bay leaf, and parsley cut into tiny pieces for the broth. Boil for a few minutes, adding salt if necessary. Pour the soup into five clay bowls. Put one slice of bread atop each, sprinkle grated cheese on top and brown in an oven.