In a stock pot, add sausage over medium-high heat. If using links, make sure to remove the casing before adding meat to the pot. Brown sausage, breaking it up into small chunks as it cooks. Once browned and cooked through, remove the sausage to a paper-towel lined plate with a slotted spoon.

Return the pan to the heat and add olive oil. Add the diced onion and cook for about 6 minutes until translucent, stirring frequently. Add crushed garlic and cook for another 2 minutes until fragrant. Pour in chicken broth plus 2 cups water, diced sweet and russet potatoes, salt and pepper. Bring to a boil, then lower to a simmer until potatoes are tender, about 15 minutes, stirring occasionally, then turn off the heat.

Using an immersion blender or a high-speed blender, puree the soup to a creamy consistency. Bring the pureed soup back to a simmer, then stir in chopped kale. Let it cook for a couple minutes to soften, then add in the sausage and parmesan cheese. Season with salt and pepper and serve with more parmesan, if desired.