Boil a large pot of salted water over high heat, add penne pasta, and cook until al dente, about 10-12 minutes. Reserve 1 cup of pasta water, then drain and set aside.

In a large skillet, heat olive oil over medium heat. Add diced onion and sauté for 3-4 minutes until translucent. Stir in minced garlic and cook for another 1-2 minutes.

Add ground beef to the skillet, breaking it apart. Cook until browned, about 6-8 minutes, seasoning with salt, pepper, and Italian seasoning.

Reduce heat to low and add heavy cream. Stir to combine. Gradually add reserved pasta water until sauce thickens. Stir in Parmesan cheese until melted.

Add drained penne to the skillet and toss until coated. Cook for an additional minute or two over low heat.

Serve hot, garnishing with extra Parmesan or parsley if desired.