Cook the Sausage: In a large pot or Dutch oven, cook the bulk Italian sausage over medium heat. Break it apart with a spoon or spatula, cooking until it is browned and cooked through, about 6-8 minutes. Remove the sausage from the pot and set it aside, leaving some of the rendered fat in the pot.

Sauté the Vegetables: Add the chopped onion to the pot and sauté in the sausage fat over medium heat until the onion is softened and translucent, about 5 minutes. This step builds flavor by allowing the onions to absorb the sausage drippings.

Prepare the Soup Base: Add the cubed potatoes to the pot along with the dried oregano, red pepper flakes, and ground black pepper. Stir well to coat the potatoes in the seasonings.

Pour in the low-sodium chicken broth and bring the mixture to a boil. Reduce the heat to a simmer and cook until the potatoes are tender, about 10-12 minutes.

Add the Dairy: Once the potatoes are tender, add the half-and-half and whole milk to the pot. Stir to combine and allow the soup to heat gently. Be careful not to let it boil, as boiling can cause the dairy to curdle.

Finish the Soup: Return the cooked sausage to the pot and add the kale. Simmer for another 5-7 minutes, or until the kale is wilted and tender. Taste and adjust seasoning as needed, adding more salt, pepper, or red pepper flakes to suit your preference.

Serve: Ladle the soup into bowls and serve hot. This soup pairs wonderfully with crusty bread for dipping or a light side salad.