In a large Dutch Oven or heavy-bottomed stockpot, heat 2 tbsp EVOO over medium-high heat. Add sausage and brown both sides (approx. 2-3 minutes per side) - do not cook them all the way through. Transfer sausages to a bowl and set aside, leaving any rendered fat or oil in the pot.
Add onion and season with a pinch of salt. Sweat onion (i.e. cook without developing colour) until soft and translucent (approx. 10-12 min).
Meanwhile, finely chop the kale into thin ribbons, discarding only the lowest stems - set aside. Also, slice the sausages into 1/2" discs - set aside.
Using an immersion blender is a real life saver in this recipe. It will keep cleaning to a minimum and is much safer than transferring piping hot liquids between pots and blenders. Click here for the model I have.