Start a pan with onions and garlic. Saute until soft but not browned.
Meanwhile, fry the sausage. Slice it if it's not crumbles. Drain excess oil.
Wash and chop the kale.
When the onions are soft and the garlic is fragrant, add potatoes and stock. Add the kale and bring to a simmer. Add the sausage and simmer until flavors meld and until the russet potato dissolves enough to thicken the stock. If you want a thicker texture, you can crush some of the russet pieces with a stirring spoon.
I made this using 1 pound of Hempler's chorizo for the sausage and was very happy with the results. The soup was mild-flavored but not boring, with the potatoes and kale providing the front notes and a delicious mild undercurrent of the chorizo spices.