6 large yellow onions cut in 1/4-inch-thick slices
2 cups water, plus 1/2 cup for deglazing
1/2 cup cooking sherry
4 cups chicken broth (or stock if you have it)
1 small baguette of french bread, cut into 1/2-inch slices
8 ounces shredded Swiss cheese (about 2 1/2 cups)
Adjust oven rack to low-middle position and heat oven to 400. Spray inside of a heavy large (7- or 8-quart) heavy pot or Dutch oven generously with nonstick spray or use more butter to coat. Place the butter in pot and add onions and 1 teaspoon salt. (*Note, if you have leftover grilled onions from, say like a concession stand cook-out or home BBQ, these work great and reduce cooking time to almost nothing!) Cook covered for for 1 hour. Remove pot from oven and stir onions, scraping bottom and sides. Return pot to the oven with the lid slightly ajar and continue cooking cook until onions are very soft and golden brown, about 1 1/2 hours longer, stirring & scraping after an hour.
Remove pot from oven and place over medium-high heat, stirring frequently, until liquid evaporates and the onions brown, about 15 minutes, reducing the heat to medium if the onions are browning too quickly. Continue to cook, stirring frequently, for 7 minutes. Pot will begin to form a dark crust.
Stir in 1/4 cup water, loosen crust, and cook until water evaporates and pot bottom has formed another dark crust, about 7 more minutes. Repeat process of deglazing 2 or 3 more times, until onions are dark brown. Stir in the sherry and cook, stirring for about 5 minutes.
Topping Croutons - While the soup simmers, arrange the bread slices in single layer on cookie sheet and bake in a 400-degree oven until crisp and golden at the edges, about 10 minutes. Set aside.
Adjust oven close to broiler and heat. Set oven-safe crocks on cookie sheet and fill each with about 1 3/4 cups soup. Top each bowl with 2 bread slices without overlapping, and add a layer of Swiss cheese. Broil until cheese is melted and bubbly around edges, about 4 minutes. Let cool 5 minutes before serving. Yummers! And delicious heated up over and over again.