Whisk cream and remaining 2 teaspoons cornstarch in now-empty bowl until cornstarch is dissolved. Whisk in water, eggs, mustard, hot sauce, Worcestershire, salt, and pepper until fully combined. Pour cream mixture over macaroni mixture in dish. Cover with aluminum foil and bake for 30 minutes.
Remove dish from oven and discard foil. Stir to redistribute macaroni. Sprinkle with remaining 1 cup cheddar. Return dish to oven and continue to bake until edges are bubbling and just set and center registers 150 to 160 degrees, about 15 minutes.
Broil until top of casserole is spotty brown, about 2 minutes. Let rest on wire rack for 25 minutes. Serve.