Heat a large Dutch oven or soup pot over medium heat. Add the chopped bacon and cook for 5 to 7 minutes, stirring occasionally, until crispy. Transfer to a paper towel-lined plate. Leave about 1 tablespoon of bacon fat in the pot.

Add the Italian sausage to the same pot. Cook for 5 to 7 minutes, breaking it into small pieces with a wooden spoon, until browned and fully cooked. Drain excess grease if needed, leaving about 1 tablespoon in the pot.

Add the diced onion and cook for 3 to 4 minutes until softened. Stir in the minced garlic and cook for another 30 seconds until fragrant.

Pour in the chicken broth, scraping the bottom of the pot to release any browned bits. Add the sliced potatoes, black pepper, optional red pepper flakes, and Italian seasoning if using.

Bring the soup to a gentle boil, then reduce the heat to medium-low. Simmer uncovered for 12 to 15 minutes, or until the potatoes are fork-tender.

Stir in the chopped kale and cook for 3 to 5 minutes until softened. Reduce the heat to low and slowly stir in the heavy cream. Warm gently for another 2 to 3 minutes without allowing the soup to boil vigorously.

Taste and add salt if needed. Ladle the soup into bowls and top with crispy bacon, freshly grated Parmesan, and additional red pepper flakes if desired.