Heat your stock pot and add the oil; cook the sausage until browned.
Removed the sausage with a slotted spoon and add the flour. Stir together and cook the flour takes on some tan to brown color - we're going after another level of flavor with the roux, not necessarily to thicken the soup.
Add the onion, carrots, & celery to the roux; cook until soft. Add the garlic & cabbage and cook until the cabbage is wilted.
Add the stock, potatoes, Italian seasoning, bay leaf, 1 tsp salt and ½ tsp black pepper.
Bring to a boil, and then down to a simmer. Simmer for 20-30 minutes until the potatoes and cabbage are done.
Taste and adjust for seasonings.
Add the sour cream and stir until evenly mixed.
Ladle into bowls, garnish, and serve with some crusty bread.