1. Heat a large skillet over medium heat and brown the spicy Italian sausage, breaking it up into small pieces until fully cooked and slightly crispy, about 6 to 8 minutes.

2. Drain off most of the fat, leaving a small amount in the skillet, then add chopped onion and cook until softened, about 3 minutes.

3. Stir in minced garlic and cook until fragrant, about 30 seconds.

4. Transfer the sausage, onion, and garlic mixture to a 6-quart crockpot and add diced tomatoes, chicken broth, Italian seasoning, red pepper flakes, salt, and pepper, then stir to combine.

5. Cover and cook on low for 5 to 6 hours or high for 3 to 4 hours to develop deep flavors.

6. About 30 minutes before serving, stir in potato gnocchi and fresh spinach, cover, and cook until gnocchi is tender and spinach is wilted.

7. Pour in heavy cream, stir gently, and cook for an additional 10 to 15 minutes until the soup is creamy and heated through.

8. Taste and adjust seasoning with salt and pepper if needed, then ladle into bowls and serve hot.