Heat olive oil in a large 12-inch skillet over medium-high heat. Brown the ground beef for 5-7 minutes, breaking it into small pieces as it cooks. Add diced onion and minced garlic, stirring constantly for 1-2 minutes until fragrant and the onion becomes translucent.

Stir in the Italian seasoning, salt, and black pepper while the beef mixture is hot. This releases the spice flavors into the meat. Pour in marinara sauce, beef broth, and diced tomatoes, stirring well to combine.

Add the uncooked pasta directly to the saucy mixture, pushing it down gently so liquid covers it. Bring everything to a gentle boil, then reduce heat to medium and simmer for 12-14 minutes, stirring occasionally so pasta doesn't stick.

Check that pasta is tender and most liquid has been absorbed into the saucy crowd pasta skillet. If it's still soupy, simmer another minute or two. Add fresh spinach and sliced mushrooms, stirring gently for 1-2 minutes until spinach wilts and mushrooms soften slightly.

Taste the dish and adjust salt and pepper if needed. Remove from heat and top with Parmesan cheese and fresh basil just before serving. Let it rest for 1 minute so flavors settle.