In a large bowl, mix together dry ingredients.
In a separate medium bowl, combine milk, buttermilk, eggs,corn and onion. Pour wet ingredients over dry ingredients and stir together just combined. Set the bowl aside to rest for one hour.
In a deep-fat fryer, or cast iron skillet, heat about 2" of oil until it reaches 360 degrees F.Drop teaspoon-sized rounds of batter into the oil. Cook for about 3 minutes or until golden brown and crispy, turning halfway through. Remove from oil and drain. Serve with hot sauce if desired.