Heat olive oil in a large non-stick saucepan over medium-high heat. Crumble the Italian sausage into bite-sized pieces and add to the pan. Cook until fully browned, stirring occasionally. Transfer the cooked sausage to a plate lined with paper towels and set aside.
In the same saucepan, add the diced bacon. Sauté for about 3 minutes, then stir in the chopped onion. Continue cooking until the bacon is crisp and the onions are soft and translucent, about 3–5 minutes.
Pour in the chicken broth and water, then add the sliced potatoes, granulated sugar, fennel seeds (if using), and a pinch of salt and black pepper. Bring the mixture to a boil, then lower the heat to medium-low. Stir in the reserved cooked sausage. Cover the saucepan and simmer until the potatoes are nearly tender, about 10–15 minutes.
Add the chopped kale and continue simmering until the potatoes are fully softened and the kale is tender, roughly 5–10 minutes. Stir in the half and half, allowing the soup to warm through. Skim any excess fat from the surface if desired.
Serve the soup hot, garnished with finely shredded Romano cheese if preferred.