In a bowl, mix cornmeal, flour, baking powder, salt, and sugar if desired
In another bowl, whisk together egg and milk or buttermilk
Add chopped onion if desired
Combine the wet and dry ingredients until just mixed
Heat oil in a deep skillet or pot to 350°F to 375°F
Drop spoonfuls of batter into the hot oil
Fry until golden brown, turning as needed
Remove with a slotted spoon and drain on paper towels
Serve warm