Pour enough oil into a deep fryer or heavy bottomed pot so the depth is 3 to 4 inches.
Heat the oil to 350 degrees.
In a medium bowl, stir together the white cornmeal mix, yellow cornmeal, buttermilk, sugar, diced onion, and salt.
Use a 1-ounce cookie scoop to drop portions of the batter into the hot oil. Fry only a few at a time for best results. If you add too many at once, the oil temperature may drop, and they make not cook well.
Fry the hush puppies for 1 to 2 minutes, until browned.
Transfer the fried hush puppies to a wire rack to drain.