Melt butter in large saucepan, add onions and fry on medium heat for 12 minutes, until golden brown. Add sugar and cook for 1 minute, stirring.
Pour the broth, cover and bring to boil. Reduce heat and simmer, without boiling, for 12 minutes.
Pour the brandy, and cook another 2 minutes. Season with salt and pepper to taste.
Pour cooked soup in bowls, put bread slices on top, sprinkle with cheese and serve immediately.
Ready in: 40 minutes.