Combine milk and vinegar in a medium bowl and set aside for 5 minutes to make sour milk.
Combine flour, sugar, baking powder, baking soda, and salt in a large mixing bowl.
Whisk egg and butter into the soured milk.
Pour flour mixture into milk mixture and whisk until lumps are gone.
Heat a skillet over medium heat and coat it with cooking spray.
Pour ¼ cupfuls of batter onto the skillet; cook until bubbles form and edges are dry, about 2–3 minutes.
Flip with a spatula and cook until browned on the other side.
Repeat with remaining batter.
