Position oven rack in upper third; preheat to 375°F. Coat a 9-by-13-inch broiler-safe baking dish with cooking spray. Heat 1 tablespoon oil in a large skillet over medium-high heat. Add 1 pound beef, 1 teaspoon each mustard, garlic powder and onion powder and ¼ teaspoon salt; cook, stirring often, until browned and crumbly, 6 to 7 minutes. Transfer to a large bowl. Wipe the skillet clean.

Place 6 cups broccoli and 5 cups water in the skillet; cook over high heat, covered, until crisp-tender, 4 to 5 minutes, stirring once. Drain the broccoli thoroughly; add to the beef in the bowl.

In a separate large bowl, combine ¾ cup Cheddar, the softened cream cheese, ½ cup sour cream, 2 teaspoons hot sauce, ¼ teaspoon pepper and the remaining 2 teaspoons mustard, 1 teaspoon each garlic powder and onion powder and ¾ teaspoon salt; stir well.

Add 2 (8.5-ounce) packages rice, ½ cup broth and the beef mixture to the cream cheese mixture; fold with a rubber spatula until evenly coated and no clumps of cheese remain. Spread the mixture in the prepared baking dish; top with the remaining ½ cup Cheddar. Cover tightly with foil. Bake until warmed through, about 30 minutes.

Remove from oven; remove foil. Increase oven temperature to broil. Broil until the cheese is bubbling and golden brown, 3 to 4 minutes. Let stand for 5 minutes. Sprinkle with ⅓ cup bacon and ¼ cup scallions.