Step 1Bring a small pot of water to a rolling boil. In a mixing bowl, combine the cornmeal, sugar, baking soda and salt and mix well. Add three-fourths cup boiling water and stir to blend well. Let cool slightly, about 10 minutes.
Step 2Add the egg, buttermilk and onion to the batter and mix well.
Step 3Coat a 10-inch cast-iron skillet with just enough bacon grease, butter or oil to cover the bottom in a glaze, about 3 tablespoons. Turn heat to medium-high.
Step 4Working in batches of three to four each, use a tablespoon to drop the batter into the pan to make small cakes. They will spread slightly as they cook. Cook 4 to 5 minutes on each side, until browned and crisp-edged. Add extra grease as necessary to keep the pan glazed while frying. Serve immediately.