Salt a large pot of water and cook the penne pasta until just al dente. Reserve one cup of pasta water, then drain the pasta.

Heat olive oil in a large skillet over medium-high heat. Add sausage and ground beef, breaking them up, and cook until browned with crispy edges. Drain excess fat if needed.

Reduce heat to medium. Stir in the butter, and once melted, add minced garlic, Italian seasoning, salt, black pepper, and red pepper flakes, if using. Cook until garlic is fragrant, about 30 seconds.

Pour in beef broth and simmer for one minute. Stir in heavy cream or half-and-half and gently bubble until the sauce slightly thickens, about 2 to 3 minutes.

Add Parmesan cheese and stir until smooth. If the sauce is too thick, add reserved pasta water a little at a time to reach desired consistency.

Add the cooked penne to the skillet and toss well to coat with the sauce. Fold in baby spinach and let it wilt from the residual heat.

Adjust seasoning with additional salt, pepper, or Parmesan cheese as desired. Add more pasta water if a looser sauce is preferred.

Garnish with fresh parsley or basil and extra Parmesan before serving.