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1
Bring beans and water (10 cups) to a boil in a 4- to 5-quart heavy pot and boil 2 minutes. Remove from heat and let stand, covered, 1 hour. (Do not drain beans or discard soaking liquid.)
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2
Heat 1/4 cup oil in a wide 6- to 8-quart heavy pot over moderately high heat until hot but not smoking, then saute onions with 1/2 teaspoon salt, stirring occasionally, until beginning to brown, 7 to 8 minutes. Add carrots, celery, garlic, parsley, rosemary, and pepper and saute, stirring occasionally, 5 minutes.
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3
Add beans with soaking liquid and Parmigiano-Reggiano rind (if using) and simmer, covered, stirring occasionally, until beans are very tender, 1 1/2 to 2 1/2 hours (depending on age of beans), adding more water if necessary to keep beans covered and stirring more frequently toward end of cooking. Remove from heat and stir in 1/4 cup oil and remaining 1 1/4 teaspoons salt. Cool, uncovered, 20 minutes.
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4
Discard rind and coarsely puree soup in batches in a blender (use caution when blending hot liquids), transferring as pureed to a large bowl.
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5
Return soup to pot and reheat over moderately low heat, stirring frequently and thinning soup as desired with additional water. Season with salt and pepper.
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6
While soup is reheating, cook pasta in a 6- to 8-quart pot of
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7
until al dente, then drain in a colander and transfer to a large bowl. Toss with remaining 2 tablespoons oil and pepper to taste.
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8
To serve, ladle soup into bowls and top with spoonfuls of pasta, then drizzle with oil.
