• Sort through 16 ounces dried navy beans, removing any broken or damaged beans and any foreign objects. Transfer the beans to a colander and rinse them under cold running water. Set aside.
• Set the Instant Pot to the "sauté" setting and add 1 tablespoon olive oil. When the oil is hot, add ½ large onion, 2 stalks celery, 2 medium carrots and stir cooking until the vegetables are softened and the onions are slightly translucent.
• Add the drained navy beans, 1 leftover ham bone or ham hock, 2 bay leaves, and 8 cups water. Seal the pressure cooker with the lid and ensure the steam valve is sealed. Pressure cook the beans for 38 minutes.
• Let the pressure reduce for 10 minutes then vent for a quick release. Remove the ham bone with a pair of tongs and transfer to a cutting board to cool. Remove the bay leaves and discard.
• Scoop about 1½ cups of the navy bean soup from the pot and transfer to a blender. Blend on high for about 15 seconds or until smooth. Transfer the purée back to the Instant Pot.
• Once the ham bone has cooled, pick off any remaining meat from the bone and shred it with a fork. Add the ham back to the pot and season with 1 teaspoon kosher salt, 1 teaspoon dried oregano, ¾ teaspoon freshly ground black pepper and ¼ teaspoon red pepper flakes. Stir to combine.
• Add 3-4 large curly kale leaves and stir into the pot. Put the lid back onto the pot and cook at high pressure for one minute. Quick release the steam from the pressure cooker. Stir to recombine. Taste and adjust for seasoning and serve.

FOR STOVETOP METHOD:

• Sort and rinse the beans as described above. Cover the navy beans with 2" of water in a large pot and either soak overnight OR use the quick soak method to rehydrate them. To quick soak, bring the beans and water to a rolling boil, cook for 2-3 minutes, remove from heat and cover tightly with a lid. Let the beans rest for one hour.
• Heat a Dutch oven over medium high heat and add one tablespoon of olive oil. When the oil is hot, add chopped onion, celery and carrots. Cook, stirring for 2-3 minutes or until the vegetables are slightly softened.
• Drain the soaked beans and add them to the pot along with the leftover ham bone or ham hock. Add the bay leaves and 8 cups of fresh water. Bring to a boil, then reduce the heat to a simmer and cook with the lid slightly askew for 2 to 2½ hours until the legumes are tender.
• Remove the ham bone and let it rest on a cutting board to cool. Remove the bay leaves.
• Puree 1½ cups of the beans and liquid in a blender until smooth. Add the puree back to the pot and season with kosher salt, oregano, black pepper, and crushed red pepper.
• Pull off any leftover meat from the ham bone and shred it with a fork. Add the ham to the pot and bring it back to a low boil. Reduce the heat to a simmer and stir in the ribbons of curly kale.
• Simmer the soup for 20-30 minutes with the lid askew, stirring occasionally to prevent it from sticking to the bottom of the pot. Taste for seasoning and adjust as necessary. Serve.