April​/May 2010

Slow-Cooker French Onion Soup

You can't caramelize onions for French onion soup without constant stirring. Or can you?

Why This Recipe Works

Soy sauce, sherry, and thyme added early on helped boost flavor of our Slow-Cooker French Onion Soup recipe, but the addition of beef bones reproduced the rich meatiness of the classic. We microwaved the bones for a few minutes before placing them in the slow cooker to simulate roasting without having to turn on the oven or dirty a roasting pan. Apple butter provided one of our favorite pork chop recipes with a silky sauce, and it had a similar effect in our Slow-Cooker French Onion Soup. Best of all, tasters never knew it was there. Because broiler-safe soup crocks are hard to come by, we opted to broil slices of bread topped with Gruyère cheese and add them to the soup at the end.


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Serves 6 to 8


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2 pounds beef bones (see note)
4 tablespoons unsalted butter
6 large yellow onions (about 4 pounds), quartered and cut into 1/4-inch-thick slices
Salt and pepper
1 tablespoon brown sugar
1 teaspoon minced fresh thyme
5 tablespoons all-purpose flour
¾ cup apple butter
¾ cup dry sherry
¼ cup soy sauce
2 cups low-sodium chicken broth
2 cups low-sodium beef broth


1 loaf French bread, cut into 1/2-inch slices
2 ½ cups shredded Gruyère cheese
Nutritional Information


Per Serving (Serves 6)

  • Calories 752
  • Cholesterol 118 mg
  • Fat 35 g
  • Sodium 1727 mg
  • Saturated 18 g
  • Carbs 65 g
  • Trans 0 g
  • Dietary Fiber 4 g
  • Monounsaturated 6 g
  • Sugar 23 g
  • Polyunsaturated 1 g
  • Protein 42 g

The information shown is Edamam’s estimate based on available ingredients and preparation. It should not be considered a substitute for a professional nutritionist’s advice.

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Serves 6 to 8

After quartering, slice the onions pole to pole for substantial slices that will hold up to long cooking (see pictures below). Beef bones are stocked in the freezer or meat section of supermarkets.

Watch the Cook's Country cast make this recipe

Play Video

1. COOK ONIONS Arrange beef bones on paper towel-lined plate. Microwave until well browned, 8 to 10 minutes. Meanwhile, set slow cooker to high. Add butter, cover, and cook until melted. Add onions, 2 teaspoons salt, 1 teaspoon peper, brown sugar, and thyme. Stir flour, apple butter, sherry, and soy sauce together in small bowl until smooth. Pour over onions and toss to coat. Tuck bones under onions around edge of slow cooker. Cover and cook on high heat until onions are softened and deep golden brown, 10 to 12 hours. (Cooked onions can be refrigerated in airtight container for 1 day.)

2. FINISH SOUP Remove bones from slow cooker. Heat chicken and beef broth in microwave until beginning to boil. Stir into slow cooker. Season with salt and pepper.

3. MAKE CROUTONS Adjust oven rack to upper-middle position (about 6 inches from broiler element) and heat oven to 400 degrees. Arrange bread slices in single layer on baking sheet and bake until bread is golden at edges, about 10 minutes. Heat broiler. Divide cheese evenly among croutons and broil until melted and bubbly, 3 to 5 minutes.

4. SERVE SOUP Ladle soup into bowls and top each with 2 croutons. Serve.

Recipe Testing

Key Ingredients: Not Very French

The bones we get. But apple butter and soy sauce?! Together, they contribute color, flavor, and silkiness.


APPLE BUTTERSilky quality

SOY SAUCEDepth and color


The Slice is Right

Most soup recipes start by chopping or mincing onions. For this recipe, we wanted slices that would retain their shape through 10 to 12 hours of gentle simmering. We found that cutting onions with the grain (rather than across it) yielded slices durable enough for the slow cooker.

1. Using a chef's knife, trim off both ends of the onion.

2. Turn onion onto cut end to steady it and slice in half, pole to pole.

3. Peel each half, place flat side down, and cut onion into slices.

Watch The Full Episode

Host Christopher Kimball shares the test kitchen’s tips and techniques for selecting the perfect beef roast. Then, test cook Bridget Lancaster shows Chris how to make the best Chuck R...