In a large pot or Dutch oven, heat a drizzle of olive oil over medium heat. Add the Italian sausage, breaking it apart with a wooden spoon. Cook until browned and cooked through, about 5-7 minutes. Drain excess fat if necessary.

Add the diced onion to the pot and sauté for 3-4 minutes until softened. Stir in the minced garlic and cook for another minute until fragrant.

Toss in the diced potatoes and pour in the chicken broth. Bring the mixture to a boil, then reduce to a simmer. Cook for about 15 minutes, or until the potatoes are tender.

Add the chopped kale and red pepper flakes (if using) to the pot. Stir well and let it simmer for another 5 minutes.

Lower the heat and carefully stir in the heavy cream. Season with salt and pepper to taste. Allow the soup to warm through for another 2-3 minutes.

Serve hot in bowls with crusty bread on the side if desired.