1Heat oil in large skillet over medium high heat til shimmering. Add pancetta and cook til lightly browned and crisp, about 8 minutes. Stir in onions, garlic and red pepper flakes and cook til onions are softened and lightly browned, 8 to 10 minutes. Stir in 1 cup broth, scraping up any browned bits; transfer to slow cooker
2Stir remaining 2 cups broth, water, soaked beans, Parmesan rind, if using, and bay leaves into slow cooker. Cover and cook til beans are tender, 9 to 11 hours on low or 5 to 7 hours on high.
3Add rosemary sprig, cover and cook on high til rosemary is fragrant, about 15 minutes. Discard rosemary, bay leaves, and Parmesan rind if using. Season with salt and pepper to taste and serve with grated Parmesan and additional olive oil.
4Salt Soaked Beans:
Pick through and rinse beans. For every pound of beans, dissolve 2 Tbsp. salt in 4 quart cold water. Mix beans and salt water in large container and let beans soak at room temperature for at least 8 hours or up to 24 hours. Drain beans, discarding the soaking liquid and rinse well before cooking. The salt tenderizes the otherwise tough and chewy beans.
For quick salt soaking, pick through an rinse beans. For every pound of beans, dissolve 3 Tbsp. salt in 2 quarts boiling water. Mix beans and hot salt water in large pot and let beans soak at room temperature for 1 hour. Drain beans, discarding soaking liquid and rinse well before cooking.