In a medium soup pot, heat 3 tablespoons of olive oil, add onions and garlic and cook for 2 to 3 minutes until they turn glassy, don't let them get brown. Add potatoes, and water. Cover and boil gently over medium heat for 20 minutes. Meanwhile, in a skillet cook sausage until most of the fat is rendered out. Drain and reserve. When the potatoes are tender mash them with a potato masher right in the pot. Add sausage to the soup, and then add the kale. Simmer for 5 minutes. Add the remaining olive oil and season. Ladle into bowls and serve.