Cooking time: 2 hours, 30 minutes
Yield: 4 to 6 servings
1/4 cup olive oil
6 medium red onions
6 cloves garlic
1 celery stalk
1 medium carrot
8 slices of pancetta or bacon (about 4 ounces)
1 teaspoon crushed red pepper flakes
1 tablespoon red wine vinegar
1 cup white wine
Salt and pepper to taste
2 1/2 quarts water or vegetable stock
1/4 cup grated Parmigiano-Reggiano cheese (optional)
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Peel the onions, cut them in half, and then slice them 1/8- to 1/4-inch thick.
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Peel and thinly slice the garlic cloves.
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Chop the celery stalk and carrot.
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Finely chop the pancetta or bacon.
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In a large soup pot, heat the olive oil over medium heat.
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Add the onions, garlic, celery, carrot, pancetta, and red pepper flakes.
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Cook for 10 to 12 minutes, stirring occasionally, until the onions are soft.
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Add the vinegar and wine.
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Cook until the liquid has almost completely evaporated, about 5 minutes.
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Season with salt and pepper.
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Add the water or broth and bring to a boil.
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Reduce the heat and simmer, loosely covered, for 2 hours (or longer, if you want).
The onions will have “melted” after 2 hours.
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Adjust the flavor with salt and pepper, if necessary.
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Sprinkle with Parmigiano-Reggiano cheese before serving, if you want.
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Ladle into large soup bowls.