Peel the onion and garlic, then slice them into thin strips. Heat some oil in a deep skillet or wok, then sauté them over medium heat, covered, until the onion becomes translucent.
The onions must not brown, or they will give your soup a bad taste.
Meanwhile, bring the amount of water listed in the ingredients to a boil. Peel the potatoes and cut them into large cubes.
Add the potatoes to the skillet and give them a stir. Then add the hot water, cover, and simmer for 20 minutes over medium heat. Season with salt and pepper to taste.
Meanwhile, rinse and slice the cabbage into thin strips (julienne).
Peel the chorizo and slice it into rounds. Sauté it over low heat for about 10 minutes to render the fat.
Remove the soup from the heat and blend it. Return it to the heat, add the chorizo and cabbage, and let it simmer for another 10 minutes.
Taste and adjust the seasoning if necessary. Serve with a drizzle of olive oil.
Notes
If some of your guests are vegetarian, this Caldo Verde is also a great option—just serve the chorizo in a separate bowl.