Take the sausages out of their casings (or just cut them up) and add them to a soup pot. Sauté them over medium-high heat for 5 minutes, stirring occasionally, until the sausage is browned on all sides. I didn't add oil since the sausages release fat, but feel free to add oil if the sausage is particularly lean.
Add the onion to the pot and continue to cook for another 4-5 minutes.
Stir in the garlic, Dijon mustard, and Italian seasoning, and cook for 30 seconds.
Add the chicken broth and gnocchi to the pot. Increase the heat to high and bring the soup to a boil. Reduce heat so it's simmering and cook for 5 minutes.
Add the kale and cream and let the soup simmer for another 10 minutes or so (you may need to increase then reduce the heat again). The gnocchi will release some starch so the broth thickens up more the longer it cooks.
Season with salt & pepper if needed.