Step 1

In a large saucepan over medium heat, cook onion and garlic in 3 tablespoons olive oil for 3 minutes. Stir in potatoes and cook, stirring constantly, 3 minutes more. Pour in water, bring to a boil, and let boil gently for 20 minutes, until potatoes are mushy.

Step 2

Meanwhile, in a large skillet over medium-low heat, cook sausage until it has released most of its fat, 10 minutes. Drain.

Step 3

Mash potatoes or puree the potato mixture with a blender or food processor. Stir the sausage, salt and pepper into the soup and return to medium heat. Cover and simmer 5 minutes.

Step 4

Just before serving, stir kale into soup and simmer, 5 minutes, until kale is tender and jade green. Stir in the remaining tablespoon of olive oil and serve at once.