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 melted butter into soured milk.

Pour flour mixture into milk mixture and whisk until lumps are gone.

Heat a large skillet over medium heat, coat with cooking spray, and pour 1/4 cupfuls of batter onto the skillet.

Cook until bubbles form and edges are dry, about 2 to 3 minutes.