Wash the collard leaves, then cut each leaf in half lengthwise by slicing down along each side of the central stem and removing it. Discard the stems. Cut each of the collard leaf halves in half again lengthwise, forming about 2-inch-wide long strips. Stack a bunch of strips on top of each other, then cut the stacks into very fine ribbons. Repeat until all the leaves are shredded. You should have about 6 to 8 cups, loosely packed. Set aside. (If using curly kale, strip out the stems, tightly bunch together handfuls of the leaves, and cut them into very fine strips as best you can.)

Heat the ¼ cup of oil in a large heavy-bottomed soup pot. Add the diced onions and sliced garlic. Cook for 3 to 4 minutes, then add the potato chunks, water, broth, 1½ teaspoons of salt, and the pepper. Cut two 1-inch chunks off the sausage and add them to the pot (this is to add flavour to the broth as it cooks). Bring the soup to a boil, then reduce the heat to medium-low, cover the pot, and simmer for 20 minutes.

While the soup is simmering, slice the remaining chorizo into ¼-inch (.5cm) slices. Heat the remaining 2 tablespoons of olive oil in a skillet over medium-high heat. Sauté the sausage slices, turning them, until they are browned on both sides and somewhat crispy. Remove the slices to a bowl, and reserve the rich, red-tinged oil from the skillet.

Remove the two chunks of sausage from the soup, slice them, and set them aside. Purée the soup with an immersion blender (or in batches in a regular blender) until silky smooth. Return the slices from the two small chunks of sausage back to the puréed soup.

Add the finely sliced collard greens or kale to the soup, increase the heat slightly, and cook for 5 to 10 minutes, until the greens are wilted and tender, but still bright green. Taste the soup and add the remaining ½ teaspoon salt and more pepper as desired, to taste. (If you use all water, you may need even more salt.) The soup should be well seasoned, as it doesn't have many ingredients, and relies on salt to bring out the flavours.

To serve, you can either add the sautéed sausage slices to the soup just before serving and stir in the flavoured sausage oil, or to be more elegant you can top each bowl with several of the sausage slices and drizzle some of the oil into each bowl at serving time.

Serves 8.