1Combine the milk and vinegar in a bowl; set aside until the milk sours, about 5 minutes.
2Stir the egg, cornmeal, salt, and baking soda into the milk mixture until evenly mixed.
3Melt some of the butter in a large skillet over medium heat. Pour 1/2 cup of the cornmeal mixture onto the skillet and cook until bubbles appear on the surface, 2 to 3 minutes. Flip with a spatula and cook until browned on the other side, 1 to 2 minutes more. Repeat until all batter is used.