French Onion Soup with Cheese Croutons

Peel the onion, cut it in half, and then slice it into approximately half-centimeter thick pieces.

In a large pot, heat the butter and oil over high heat and add half of the onion. Fry intensely and quickly until the onion begins to turn golden in places. Color is important, so stir and continue frying until there is a risk of burning. At that point, pour a few tablespoons of water over the onion to dissolve the caramelized bits from the bottom of the pot. This will delay burning, and as soon as the water evaporates, you can continue frying. Repeat this process two or three more times until the onion has a uniform golden color.

After the first half of the onion is fried, add the rest and let it soften, stirring constantly. This time you don't need to let it turn golden. This method will give the soup a more interesting texture. Finally, add the sugar and stir for another minute until it dissolves.