Onion soup from the slow cooker

This isn't a fix-it-and-forget-it recipe, at least not in the beginning, but it's an easier way to make a big pot of onion soup.

You'll need to soften the onions on the stove, then cook them for a couple of hours on high in the slow cooker. I stirred in a little bit of tomato paste to promote caramelization and add flavor, a technique I borrowed from a brisket recipe in America's Test Kitchen's wonderful "Slow Cooker Revolution."

Once you stir in the stock, you can cook the soup on high heat for 3 to 4 hours or on low for 6 to 8 hours.

Be sure to buy yellow onions, not sweet onions, which can be watery. You can use chicken stock or beef stock or combine the two, as I did.

By the way, this recipe was inspired by a St. Louis favorite, Famous-Barr French Onion Soup. I got the recipe (and bought the trademark crocks, pictured above) when I worked there as a teenager. I'm providing that vintage recipe at the bottom of this post, complete with my notations for cutting the recipe in half, although I soon learned that leftover soup was something to be welcomed, not avoided.


SLOW-COOKER ONION SOUP

Yield: 8 to 10 servings

2 tablespoons butter or ghee
3 pounds yellow onions, peeled and sliced thinly
1/2 tablespoon tomato paste
1/2 teaspoon ground black pepper
4 tablespoons all-purpose flour
1 bay leaf
1 quart beef stock
1 quart chicken stock
Salt, optional
1 loaf French bread
Grated Swiss and/or Gruyere cheese

If your slow cooker has a nonstick insert that can be placed directly on the stove, set over medium-high heat. Otherwise, use a large nonstick pot. Melt the butter, then add the onions. Cook, stirring frequently, until the onions soften, about 8 minutes. Add tomato paste and black pepper and stir until well combined.

Place the insert in the slow cooker or transfer the onions from the pot to the slow cooker. Cover and cook on high for about 2 hours or until the onions are golden.

Sprinkle with 1 tablespoon flour; stir until no lumps remain. Repeat with remaining flour, 1 tablespoon at a time. Add bay leaf; stir in stock. Cover and cook for 3 to 4 hours on high or 6 to 8 hours on low. Taste; add salt if desired.

To serve, slice the bread about 1/2-inch thick. Arrange on a cookie sheet; sprinkle with cheese. Place under a hot broiler until the cheese melts and starts to brown. Ladle soup into bowls. Top each serving with a slice or two of cheese-topped bread. (Alternately, ladle soup into bowls that can withstand the heat of a broiler. Arrange on a cookie sheet. Top each bowl with bread and cheese. Place under a hot broiler until the cheese melts and starts to brown, about 1 to 2 minutes.)