Preheat your oven to 425°F (220°C).
In a medium bowl, prepare the biscuit topping by mixing together the Cheddar Bay Biscuit Mix, water, and 1 cup shredded cheddar cheese until just combined. Set aside.
In a large oven-safe skillet (12-inch cast iron works great), brown the ground beef with diced onions over medium-high heat, breaking it into small pieces as it cooks.
Once the beef is fully cooked (no pink remains), drain any excess grease from the pan.
Season the beef mixture with onion powder, garlic powder, salt, and black pepper, stirring to combine.
Reduce heat to low and stir in the cream of mushroom soup, sour cream, and remaining 1 cup of shredded cheddar cheese until everything is well incorporated and creamy.
Using a large spoon or cookie scoop, drop portions of the biscuit dough evenly over the top of the beef mixture, creating 5-6 biscuit mounds.
Transfer the skillet to the preheated oven and bake for 20-30 minutes, or until the biscuits are golden brown and cooked through.
While the casserole bakes, mix together the melted butter and garlic herb blend in a small bowl.
When the casserole comes out of the oven, immediately brush the garlic butter mixture over the warm biscuits.
Let cool for 5 minutes before serving to allow the sauce to thicken slightly.