There are "side soups," and then there are "meal soups," and Caldo Verde is definitely the latter. Portuguese Green Soup features kale and chorizo in a silken broth, thickened by Russet potatoes. Brown your sausage first to coax out the best flavor. Build your base by adding sautéed onion and garlic, potatoes, and kale into bone broth. Add your sausage after simmering, and serve it steaming with fresh bread.
Heat a dutch oven over medium high heat. Add 1 tablespoon olive oil and heat until shimmering. Add the sausage links and saute 3-4 minutes per side, until well browned. Remove using tongs and set aside.
Add the onion and garlic and toss to coat in the fat. Saute, stirring occasionally, until soft, 8-10 minutes.
Add the potatoes and broth, then season with salt and pepper. Adjust the heat to maintain a brisk simmer. Cover and simmer 15 minutes, or until the potatoes are releasing their starch and starting to fall apart.
Add the kale. Simmer 15-20 minutes more, or until the kale is very soft, the potatoes are disintegrating, and the soup takes on a thickened, slightly creamy consistency. Optional: use a stick blender to slightly puree the soup (just a few quick rounds) or remove ⅓ of the soup and puree in a blender.
Slice the sausage links into coins and return them to the pot. Simmer 5 minutes, or until the sausages are cooked through.
Taste for seasoning and adjust with salt and pepper as needed. Ladle into soup bowls and garnish with red pepper flakes for a spicier finish. Serve immediately.