Crisp the bacon: Add chopped bacon to a large pot over medium heat. Cook until crisp, 6–8 minutes. Transfer to a paper towel–lined plate. Leave about 1 tablespoon fat in the pot.
Brown the sausage: Add sausage. Break it into crumbles and cook until browned and cooked through, 6–8 minutes. If the pan looks dry, add a splash of olive oil. Spoon off excess fat, leaving about 1–2 tablespoons for flavor.
Soften aromatics: Add the diced onion and a pinch of salt. Cook 3–4 minutes until translucent. Stir in garlic and a pinch of red pepper flakes. Cook 30 seconds until fragrant.
Simmer the potatoes: Pour in the chicken broth and scrape up browned bits. Bring to a boil. Add sliced potatoes. Reduce to a lively simmer and cook 10–12 minutes, stirring occasionally, until the potatoes are tender when pierced but not falling apart.
Add the greens: Stir in chopped kale. Simmer 2–4 minutes until softened and bright green.
Make it creamy: Lower the heat. Stir in heavy cream and half the crispy bacon. Warm through 1–2 minutes. Do not boil after adding cream.
Finish and season: Taste and season with salt and black pepper. If you like heat, add a pinch more red pepper flakes.
Serve: Ladle into bowls. Top with remaining bacon, Parmesan, and a squeeze of lemon if you like. Add crusty bread for dunking.
