Remove sausage from casing.
In an 8 quart stock pot or Dutch oven, brown sausage.
Use a slotted spoon to remove from pan.
Add olive oil to pan.
Heat until shimmering.
Add onions, celery, carrots, and garlic.
Sauté over medium heat until vegetables are tender.
Add Italian seasoning.
Cook 1-2 minutes.
Add lentils, sausage, potatoes, and broth.
Bring to a boil.
Reduce heat to simmer.
Cook 20-30 minutes, until lentils are cooked and potatoes are tender.
Stir in kale.
Cook an additional 10 minutes.
Season to taste with salt and pepper, if desired.