Preheat and prep: Heat your oven to 375°F (190°C).
Grease a 9x13-inch baking dish with nonstick spray or butter.
Cook the pasta: Bring a large pot of salted water to a boil. Cook the pasta to just shy of al dente, about 1 minute less than package directions. Drain and set aside.
Brown the beef: Heat olive oil in a large skillet over medium-high.
Add the ground beef and break it up with a spatula. Cook until browned with crispy bits, about 6–8 minutes. Season with salt and pepper.
Add aromatics: Stir in the diced onion and cook 3–4 minutes until softened.
Add garlic and cook 30 seconds until fragrant.
Season it up: Sprinkle in smoked paprika, Italian seasoning, mustard powder, and a pinch of red pepper flakes if using. Stir to coat the beef.
Sauce shortcut: Pour in the marinara and Worcestershire sauce. Simmer 2–3 minutes to meld flavors.
Taste and adjust salt and pepper.
Cheesy base: Reduce heat to low. Add butter and milk, stirring until the butter melts and the sauce looks creamy. Stir in 1½ cups cheddar and all the mozzarella until just melted and smooth.
Combine with pasta: Add the drained pasta to the skillet and fold everything together so the noodles are well coated.
Into the dish: Transfer the mixture to the prepared baking dish.
Smooth the top and sprinkle over the remaining ½ cup cheddar.
Bake: Place on the middle rack and bake 15–20 minutes, until the cheese on top is melted and lightly bubbling at the edges.
Finish and rest: Let the bake rest 5 minutes so it sets slightly. Garnish with chopped parsley or green onions. Serve warm.