I've never met a French Onion soup I didn't adore. I've made several different recipes through the years from fancy-schmancy (including roasting beef bones to make the stock) to this, the simplest I've ever made.
It came out of a James Peterson cookbook, Splendid Soups. Ironically, I'd never used this recipe because this book is a wee bit intimidating to me (lots of fancy titles and some exotic ingredients). But this recipe called just a handful of ingredients.
At first I was afraid this 2 1/2 pounds of sliced onions seemed a tad overload. But being the onion lover I am, it came out perfectly. I suppose you could scale it down to 1 1/2 to 2 pounds, but why would you?!!!
FRENCH ONION SOUP (4-5 servings)
2 1/2 pounds onions, peeled (I used primarily sweet onions and a little red onion)
2 Tbsp unsalted butter
32 oz box of reduced-sodium beef broth
1 bouquet garni (3 sprigs fresh thyme, 3 sprigs parsley, 1 bay leaf)
1 cup finely grated Swiss Gruyere (I used regular Swiss), about 1/4 pound
4 thick slices of French bread (I cut mine from a Panera French baguette), toasted
Slice onions as thinly as possible (I used a mandolin slicer). Melt the butter in a wide, heavy-bottomed pot and add the onions. Stir the onions every few minutes over medium heat until they soften and begin to brown, about 40 minutes. When they start to brown, pour in 1/2 cup broth and turn the heat to high.
Stir the onions, scraping off any caramelized juices that have clung to the bottom and sides of the pan. When the broth has completely evaporated and forms a brown glaze on the bottom of the pan, add another 1/2 cup broth and repeat.
Add the remaining broth and the bouquet garni to the onions and gently simmer the soup for 15 minutes. Be sure to scrape the pan so the caramelized juices dissolve in the soup. Season to taste with S&P and remove the bouquet garni.
At the last minute: Preheat the oven to 400 F (I put mine on high broil). Ladle the soup into deep bowls. Sprinkle half the cheese over the soup and place a slice of toast in each
bowl. Sprinkle with remaining cheese. Put the bowls on a sheet pan and bake (or broil) until the cheese bubbles and turns light brown.
Recipe Adapted from: Splendid Soups by James Peterson, 2001, p. 200