Heat 2 inches of oil in a large Dutch oven over medium to 350°F. Meanwhile, grate frozen butter using the large holes of a box grater into a medium bowl; transfer butter to freezer. Grate onion using the large holes of box grater; squeeze onion in a double layer of paper towels to remove as much liquid as possible. Reserve 1/2 cup squeezed grated onion; discard any remaining grated onion or reserve for another use.

Whisk together cornmeal, flour, baking powder, sugar, salt, pepper, garlic powder, and onion powder in a large bowl until well combined. Whisk together buttermilk, eggs, and grated onion in a separate medium bowl until well combined. Pour buttermilk mixture over cornmeal mixture, and top with frozen grated butter. Fold together until just combined. Batter will be a thick pancake batter consistency.

Working in batches, drop spoonfuls of batter (about 1 1/2 tablespoons each) into hot oil, being careful not to overcrowd. Cook, turning occasionally, until crispy, golden brown and cooked through, about 3 minutes. Transfer hush puppies to a paper towel–lined baking sheet. Sprinkle with additional salt and pepper to taste. Serve hot.