In a small bowl, combine the milk and vinegar and let sit for 10 minutes to “sour”; set aside.
This is an important step and it is called “soured milk” which is much different that sour milk.
In a medium bowl, combine the dry ingredients.
In a smaller bowl, whisk the soured milk, egg, vanilla and melted butter together.
Pour into the dry ingredients and whisk until most of the lumps are gone, but do not over beat!; the batter will be thick, don’t add any more liquid.
Let the batter sit undisturbed for 10 minutes.
After 10 minutes, you will see bubbles in the batter; it is very important you do not stir again.
Gently dip out – don’t pour out – 1/2 cup of batter and place it on a buttered grill or frying pan.
Cook until bubbles appear on the surface of the pancake and then flip, with a spatula, and brown the other side.