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1
Put the 1 tablespoon olive oil in a Dutch oven over medium heat. Add the sausage, breaking up with a spoon, and cook for about 10 minutes until the fat is rendered and the sausage is well-browned. Remove the sausage bits and set aside.
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2
Add the onion, bell pepper, celery, carrots, fennel, and 1 teaspoon salt. Adjust the heat to medium and cook, stirring occasionally, for at least 10 minutes, or until the vegetables are softened.
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3
Add the tomato paste, stirring well to coat the vegetables, and cook for about 2 minutes to melt the paste. Add the garlic, tomatoes, lentils, water, cheese rinds, and bay leaf. Turn the heat to high, bring to a boil, and then reduce the heat to medium-low. Simmer for 30 minutes. Remove and discard the bay leaf and cheese rinds.
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4
Place the 1 cup cheese in a blender. Add about one-third of the soup to the blender and puree the soup and cheese, making sure that your blender is less than one-third full. Return the puree to the pot. Add the reserved sausage bits, stir to combine, and add the balsamic vinegar. Taste for seasoning, adding salt and pepper if desired. Serve with bread, additional grated Parmesan, and a drizzle of extra virgin olive oil.
