Preparation

• Put the beans in a large pot with enough water to cover by 2 inches. Bring to a boil over high heat, cover, remove from the heat, and let soak for 1 hour. (Alternatively, soak the beans refrigerated in ample water overnight.) Drain the water from the beans, cover with fresh water by 2 inches, and bring to a boil over medium-high heat. Reduce to a simmer, and cook until tender, about 30 minutes.
• Position a rack in the center of the oven and heat to 400°F.
• Put the sweet and russet potatoes in a large bowl and toss with 2 Tbs. of the oil, 2 tsp. salt, and 1/4 tsp. black pepper. Spread in a single layer on a rimmed baking sheet, and roast until slightly tender and just beginning to brown, about 15 minutes.
• Meanwhile, heat 2 Tbs. of the oil in a large skillet over medium-high heat. Cook the kale, stirring and adding it in batches as the leaves begin to wilt, about 6 minutes. Season with 1/2 tsp. of salt. Transfer to a bowl.
• Heat 2 Tbs. of the remaining olive oil in the skillet over low heat. Add the onion and cook, stirring occasionally, until tender, 10 to 15 minutes. Transfer the cooked onion to a blender with 3 Tbs. of the vegetable stock, and process until smooth.
• Turn the oven down to 350°F.
• Heat 6 Tbs. of the oil in a 4-quart Dutch oven over medium heat. Add the shallots and cook, stirring, until lightly browned, about 3 minutes. Add the beans and the remaining 4 cups stock, and bring to a simmer over medium-high heat. Stir in the butter and the onion purée. Cover the pot and bake until the beans soak up some of the liquid and become more tender, about 30 minutes.
• Remove the pot from the oven, and stir in the roasted potatoes, kale, lemon juice, and jalapeños. Season to taste with salt and pepper.
• Return to the oven and bake until the beans have absorbed most of the liquid and a crust has formed on top, 45 to 60 minutes.
• Toss the panko with the remaining 2 Tbs. oil, 2 Tbs. of the parsley, 1/4 tsp. salt, and 1/4 tsp. pepper. Toast in a large skillet over medium-high heat, stirring frequently, until golden, about 3 minutes.
• Sprinkle the top of the cassoulet with the remaining parsley, top with the panko, return to the oven, and bake until browned, about 10 minutes. Let rest for about 30 minutes before serving.