MELT butter in large saucepan on medium heat. Whisk in flour; cook and stir 1 minute. Gradually stir in milk, whisking constantly until thickened. Reduce heat to low. Add 1/3 cup of the RedHot Sauce and cheese, stirring until melted. Remove from heat. Remove 1/2 cup cheese sauce and place in small microwave-safe bowl; set aside.
ADD 1 egg to remaining cheese sauce in saucepan, stirring to mix well. Add cooked macaroni, stirring gently to coat. Spread mixture evenly in 13x9-inch pan. Cover. Refrigerate at least 4 hours.
POUR 2 inches of oil into large deep skillet. Heat oil to 350°F on medium heat. Whisk remaining 3 tablespoons RedHot Sauce and remaining egg in small bowl. Place panko in separate shallow dish. Scoop cold mac & cheese mixture into about 24 heaping tablespoonfuls and roll into balls. Dip in egg mixture, shaking gently to remove excess. Then roll in panko to coat. Repeat until all mac & cheese balls are coated.
WORKING in batches, gently place mac & cheese balls in hot oil, being sure not to over-crowd the oil. Cook until crispy and golden brown, about 2 to 3 minutes. Transfer to paper towel-lined plate to drain.
RE-HEAT reserved cheese sauce in microwave 1 to 2 minutes, or until heated through, stirring every 30 seconds. Serve Mac & Cheese bites with hot cheese sauce for dipping.