Caramelized Maui Onion Soup

Ingredients - 
3 cups Maui onion, peeled and slice 
1/2 cup sugar 
1/2 cup clarified butter, see recipe 
4 tbsp dry sherry wine 
4 tbsp white wine 
2 liters chicken stock 
1/2 cup Parmesan cheese, grated 
salt and pepper to taste 
2 cups sourdough croutons, diced and toasted
Procedure - 
In a large bowl, combine the onions, sugar and salt and stir to mix well. In a large heavy saucepan over high heat, heat the butter until almost smoking. Add the onions and stir until the onions begin to brown, about 3 minutes. Reduce heat to low and stir until the onions are soft and golden brown. Stir in the white wine and sherry. Return the caramelized onions to the stove and add the strained stock. Bring to a boil, reduce heat to medium, and cook to reduce to about 6 cups. Simmer for 5 to 10 minutes. Season with salt and pepper and serve with cheese and croutons.