Bring a large pot of salted water to a boil. Add 8 ounces of elbow macaroni and cook according to package instructions until al dente. Drain and set aside.
Heat 1 tablespoon of olive oil in a large skillet over medium-high heat. Add 1 pound of ground beef and cook, breaking it up with a spatula, until browned and cooked through, about 6-8 minutes. Drain any excess fat.
Sprinkle 1 teaspoon each of garlic powder, onion powder, smoked paprika, and black pepper over the browned beef. Stir to coat evenly, letting the spices toast slightly for about 1 minute.
Lower the heat to medium. Add 1 cup beef broth and 1 cup whole milk to the skillet with the beef. Stir to combine and bring to a gentle simmer. Gradually stir in 2 cups shredded cheddar cheese and 1 cup shredded mozzarella cheese until fully melted and smooth.
Remove the skillet from heat. Stir in 1/2 cup sour cream and 1/2 cup chopped scallions to add creaminess and fresh flavor.
Add the drained elbow macaroni to the cheese and beef mixture. Stir until the pasta is fully coated and everything is evenly combined.
Transfer the mac and cheese mixture to a serving dish or bake in a preheated oven at 350°F (175°C) for 10-15 minutes if you want a bubbly hot dish. Just before serving, sprinkle 1 cup of crispy fried onions on top for that signature crunch.
Garnish with extra scallions if desired and serve immediately. Perfect alongside a fresh salad or Honey Sriracha Coleslaw for a balanced meal.