This soup comes together easily as the kale simmers to a perfect, just-tender texture and potatoes add body to a quick but flavorful broth.
1 tablespoon extra-virgin olive oil
1 pound dry-cured linguiça sausage or Spanish chorizo, sliced into 1/4-inch-thick half-moons (about 1 1/3 cups)
1 small (7 ounce) yellow onion, chopped (1 1/2 cups)
4 large garlic cloves, finely chopped (about 2 tablespoons)
3 fresh bay leaves
1/2 teaspoon black pepper
1/2 teaspoon kosher salt, divided, plus more to taste
2 quarts lower-sodium chicken broth
3/4 pounds lacinato kale, thick stems removed, cut into strips (about 8 packed cups)
2 pounds russet potatoes, peeled, quartered, and cut into 1-inch pieces (about 6 cups)
2 teaspoons white vinegar
Heat oil in a large Dutch oven over medium-high. Add linguiça or chorizo in an even layer; cook just until sausage begins to crisp, 1 to 2 minutes per side. Remove from heat. Transfer sausage to a paper towel–lined plate using a slotted spoon. Reserve 2 tablespoons drippings in Dutch oven; discard remaining drippings. Add onion, garlic, bay leaves, pepper, and 1/4 teaspoon salt to drippings in Dutch oven; heat over medium. Cook, stirring often, until onion is softened, about 4 minutes.
Add broth, kale, and potatoes to Dutch oven. Bring to a vigorous simmer over medium-high, stirring to submerge kale in chicken broth. Reduce heat to low; simmer, stirring occasionally, until the kale is very tender but still has some texture and the potatoes are very tender and are starting to break down in broth, 35 to 40 minutes. Mash about 1/2 cup potatoes against the sides of the Dutch oven to thicken soup. Stir in vinegar, reserved sausage, and remaining 1/4 teaspoon salt. Season with additional salt to taste.
