01 - Preheat oven to 350°F (177°C).
02 - Heat a large nonstick skillet over medium-high heat. Add ground beef and diced onion, breaking up the meat while cooking. Sauté until beef is thoroughly browned and onions are softened.
03 - Stir in chopped garlic, condensed cheddar soup, condensed cream of mushroom soup, 0.5 cup milk, salt, and ground black pepper. Mix until completely combined. Incorporate 1 cup of shredded cheddar cheese, stirring until melted. Remove from heat.
04 - Coat a 9 x 13-inch baking dish with cooking spray. Evenly spread the beef mixture in the prepared dish and top with the remaining 1 cup shredded cheddar cheese.
05 - Empty biscuit mix into a large mixing bowl, setting aside the included seasoning packet. Blend in 1 cup shredded cheddar cheese and 2 cups milk, stirring until the batter is smooth and no large lumps remain.
06 - Pour the biscuit batter evenly over the beef mixture in the baking dish.
07 - Transfer the dish to the oven and bake for 50–55 minutes, or until the biscuit topping is golden brown throughout.
08 - Thoroughly combine melted butter with the reserved Cheddar Bay Biscuit seasoning packet.
09 - Remove casserole from oven. Immediately brush the butter-seasoning mixture over the biscuit topping. Allow to rest 5 minutes before garnishing with fresh chopped parsley and serving.