In a large pot, heat the olive oil over medium heat. Add the Italian sausage and cook until browned, breaking it up with a spoon, about 5-7 minutes.
Add the diced onion and minced garlic to the pot. Sauté for another 3-4 minutes until the onion is translucent.
Pour in the chicken broth and bring to a boil. Add the diced potatoes, thyme, oregano, salt, and pepper. Reduce heat and simmer for about 15-20 minutes, or until the potatoes are tender.
Stir in the chopped kale (or spinach) and cook for an additional 5 minutes until wilted.
If using, stir in the heavy cream and heat through. Adjust seasoning if necessary.
Serve hot, topped with grated Parmesan cheese if desired.