Combine milk with vinegar in a medium bowl and set aside for 5 minutes to "sour".
Combine flour, sugar, baking powder, baking soda, and salt in a large mixing bowl. Whisk egg, butter, and vanilla into "soured" milk. Pour the flour mixture into the wet ingredients and whisk until lumps are gone.
Heat a large skillet over medium heat, and coat with cooking spray. Pour 1/4 cupfuls of batter onto the skillet, and cook until bubbles appear on the surface. Flip with a spatula, and cook until browned on the other side.