Step 1: In a large pot or Dutch oven, cook the chopped bacon over medium heat until crispy. Remove the bacon with a slotted spoon and set aside, leaving about 1-2 tablespoons of bacon grease in the pot.
Step 2: Add the crumbled Italian sausage to the pot with the bacon grease. Cook over medium-high heat, breaking it apart with a spoon, until thoroughly browned. Drain excess fat if desired, then remove the sausage and set aside with the bacon.
Step 3: Add the diced onion to the pot and cook in the remaining fat for 3-5 minutes, until softened and translucent. Add the minced garlic and red pepper flakes (if using), and cook for another minute until fragrant.
Step 4: Pour in the chicken broth and water, then add the diced potatoes, black pepper, and salt. Bring the mixture to a boil, then reduce heat to a simmer, cover, and cook for 15-20 minutes, or until the potatoes are tender.
Step 5: Stir in the cooked Italian sausage and the fresh kale. Continue to simmer for 3-5 minutes, or until the kale has wilted.
Step 6: Reduce the heat to low and stir in the heavy cream. Heat through gently, but do not bring to a rolling boil after adding the cream. Taste and adjust seasoning as needed.
Step 7: Ladle the Zuppa Toscana into bowls. Garnish each serving with the crispy bacon bits before serving hot.