Preheat the oven to 375°F. Grease a 13-by-9-inch baking dish with the oil.
Bring a large pot of salted water to a boil and cook the pasta for 1 minute less than the package directions. Drain and set aside.
In a large sauté pan or Dutch oven, heat the oil over medium heat. Add the ground beef, bell pepper, and onion and cook, breaking up the beef with a wooden spoon, until the beef browns and the vegetables start to turn golden, 10 to 12 minutes. Add the garlic, paprika, pepper, and 1 ½ teaspoons salt and cook until fragrant, about 1 minute. Add the beef broth, tomato sauce, mustard, and Worcestershire sauce. Bring to a boil, then reduce the heat to medium-low and simmer until the sauce is slightly reduced, about 5 minutes.
Remove the pan from the heat and whisk in the cream cheese and milk. Fold in 1 cup of the pepper jack cheese, and then the green onions and pasta.
Transfer the pasta mixture to the prepared baking dish, sprinkle with the remaining 1 cup pepper jack cheese and the fried onions, and bake until golden and bubbly, 20 to 25 minutes. Sprinkle with more green onions and serve.
