Caramelized Four Onion Soup

For those of you with storage shares, it’s probably best to eat your alliums as soon as possible; this is not going to be a good year for keeping them!
-Heat 2 TBS butter and 2 TBS olive oil in a soup pot over medium heat.
-Thinly slice into rings 2-3 medium yellow onions, 1 red onion, 2 large shallots and 1 leek.  
-Add to the pot and cook over low heat for 45 minutes, stirring occasionally until caramelized.
-Then stir in ¼ cup dry sherry or cognac, increase the heat to high and add 4 cups beef, chicken or vegetable stock.  
-Bring to a boil, reduce heat and simmer for 20 minutes, partially covered.
-Season with salt and black pepper.
-Spread 8 pieces of French bread with a little butter and toast until lightly brown.
-Grate 1 cup Gruyere cheese.
-Place 8 ovenproof soup bowls on a baking sheet.
-Fill each bowl with soup and top with a slice of bread and some cheese.
-Bake or broil in a 450-degree oven until cheese melts.