Melt 2 tablespoons butter in heavy large pot over medium-high heat. Add yellow onions and cook until very soft and caramelized, stirring frequently, about 40 minutes. Add wine and Sherry and bring to boil, scraping up any browned bits. Add stock, Worcestershire, the, oregano, pepper and bay leaf. Reduce heat and simmer soup 30 minutes, stirring occasionally. Melt remaining 1 tablespoon butter in heavy medium skillet over medium heat. Add shallots, green onions and garlic and cook until golden, stirring frequently, about 10 minutes. Add to soup and stir to combine. (Can be prepared 1 day ahead. Cover and refrigerate. Bring to simmer before continuing.) Preheat broiler. ladle soup into 4 broiler-proof soup crocks. Top each with 2 toasted bread slices and 2 cheese slices. Broil until cheese bubbles. soup 44