Heat olive oil in a large skillet over medium heat. Add the Italian sausage, breaking it up with a spoon. Cook until fully browned and cooked through, about 5–7 minutes. Remove any excess grease if needed.
Stir in the minced garlic, Italian seasoning, and crushed red pepper flakes. Cook for about 30 seconds, just until fragrant. This step builds flavor, so don’t skip it!
Pour in the diced tomatoes (with their juices), chicken broth, and heavy cream. Stir everything together, scraping any browned bits from the bottom of the pan for added flavor. Let it come to a gentle simmer.
Add the gnocchi directly to the skillet and stir to coat. Cover the pan (or partially cover if it’s bubbling too much) and let it simmer for 6–8 minutes, stirring occasionally, until the gnocchi are tender and cooked through.
Once the gnocchi are soft, stir in the spinach or kale, if using. Let it wilt for 1–2 minutes. Then add the grated Parmesan cheese and stir until the sauce is creamy and well combined.
Taste and adjust seasoning with salt and pepper. Spoon the creamy gnocchi into bowls and top with extra Parmesan and fresh herbs if desired. Serve immediately while hot and bubbly.