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Best French Onion Soup

By Cook's Illustrated Published January 2008

Why This Recipe Works

With too many onion soups, digging through a layer of congealed cheese unearths a disappointing broth that just doesn’t taste like onions. The ideal French onion soup combines a satisfying broth redolent of sweet caramelized onions with a slice of toasted baguette and melted cheese. We wanted a foolproof method for achieving extraordinarily deep flavor from the humble onion—the star of this classic soup.

The secret to a rich broth was to caramelize the onions fully. The good news is that caramelizing the onions, deglazing the pot, and then repeating this process dozens of times will keep ratcheting up the flavor. The bad news is what a laborious, hands-on process this proved to be. Fortunately, we found that if we first cooked the onions covered in a hot oven for two and a half hours, we only needed to deglaze the onions on the stovetop three or four times. Just one type of onion (yellow) was sufficient, but a combination of three different liquids (water, chicken broth, and beef broth) added maximum flavor. For the topping, we toasted the bread before floating it on the soup to ward off sogginess and added only a modest sprinkling of nutty Gruyère so the broth wasn’t overpowered.

Ingredients

1 1/2 pounds fresh sweet cherries, pitted and halved
1 teaspoon lemon juice
2 teaspoons all-purpose flour, plus 1/2 cup (2 1/2 ounces)
1/8 teaspoon ground cinnamon
4 large eggs
2/3 cup (4 2/3 ounces) plus 2 teaspoons sugar
2 1/2 teaspoons vanilla extract
1/4 teaspoon salt
1 cup heavy cream
2/3 cup whole milk
1 tablespoon unsalted butter

Instructions

Serves 6

We prefer whole milk in this recipe, but 1 or 2 percent low-fat milk may be substituted. Do not substitute frozen cherries for the fresh cherries.

1. Adjust oven racks to lowest and upper-middle positions; place 12-inch skillet on lower rack and heat oven to 425 degrees. Line rimmed baking sheet with aluminum foil and place cherries, cut side up, on sheet. Roast cherries on upper rack until just tender and cut sides look dry, about 15 minutes. Transfer cherries to medium bowl, toss with lemon juice, and let cool for 5 minutes. Combine 2 teaspoons flour and cinnamon in small bowl; dust flour mixture evenly over cherries and toss to coat thoroughly.

2. Meanwhile, whisk eggs, 2/3 cup sugar, vanilla, and salt in large bowl until smooth and pale, about 1 minute. Whisk in remaining 1/2 cup flour until smooth. Whisk in cream and milk until incorporated.

3. Remove skillet (skillet handle will be hot) from oven and set on wire rack. Add butter and swirl to coat bottom and sides of skillet (butter will melt and brown quickly). Pour batter into skillet and arrange cherries evenly on top (some will sink). Transfer skillet to lower rack and bake until clafouti puffs and turns golden brown (edges will be dark brown) and center registers 195 degrees, 18 to 22 minutes, rotating skillet halfway through baking. Transfer skillet to wire rack and let cool for 25 minutes. Sprinkle clafouti evenly with remaining 2 teaspoons sugar. Slice into wedges and serve.

4. Adjust oven racks to lowest and upper-middle positions; place 12-inch skillet on lower rack and heat oven to 425 degrees. Line rimmed baking sheet with aluminum foil and place cherries, cut side up, on sheet. Roast cherries on upper rack until just tender and cut sides look dry, about 15 minutes. Transfer cherries to medium bowl, toss with lemon juice, and let cool for 5 minutes. Combine 2 teaspoons flour and cinnamon in small bowl; dust flour mixture evenly over cherries and toss to coat thoroughly.

5. Meanwhile, whisk eggs, 2/3 cup sugar, vanilla, and salt in large bowl until smooth and pale, about 1 minute. Whisk in remaining 1/2 cup flour until smooth. Whisk in cream and milk until incorporated.

6. Remove skillet (skillet handle will be hot) from oven and set on wire rack. Add butter and swirl to coat bottom and sides of skillet (butter will melt and brown quickly). Pour batter into skillet and arrange cherries evenly on top (some will sink). Transfer skillet to lower rack and bake until clafouti puffs and turns golden brown (edges will be dark brown) and center registers 195 degrees, 18 to 22 minutes, rotating skillet halfway through baking. Transfer skillet to wire rack and let cool for 25 minutes. Sprinkle clafouti evenly with remaining 2 teaspoons sugar. Slice into wedges and serve.

7. Adjust oven racks to lowest and upper-middle positions; place 12-inch skillet on lower rack and heat oven to 425 degrees. Line rimmed baking sheet with aluminum foil and place cherries, cut side up, on sheet. Roast cherries on upper rack until just tender and cut sides look dry, about 15 minutes. Transfer cherries to medium bowl, toss with lemon juice, and let cool for 5 minutes. Combine 2 teaspoons flour and cinnamon in small bowl; dust flour mixture evenly over cherries and toss to coat thoroughly.

8. Meanwhile, whisk eggs, 2/3 cup sugar, vanilla, and salt in large bowl until smooth and pale, about 1 minute. Whisk in remaining 1/2 cup flour until smooth. Whisk in cream and milk until incorporated.

9. Remove skillet (skillet handle will be hot) from oven and set on wire rack. Add butter and swirl to coat bottom and sides of skillet (butter will melt and brown quickly). Pour batter into skillet and arrange cherries evenly on top (some will sink). Transfer skillet to lower rack and bake until clafouti puffs and turns golden brown (edges will be dark brown) and center registers 195 degrees, 18 to 22 minutes, rotating skillet halfway through baking. Transfer skillet to wire rack and let cool for 25 minutes. Sprinkle clafouti evenly with remaining 2 teaspoons sugar. Slice into wedges and serve.

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