Into a large bowl, sift the flour, sugar, baking soda, and salt. Set aside. In a separate bowl or large measuring cup, mix together the milk and vinegar and let sit for 2 minutes to curdle.
Pour in the butter, vanilla, and egg and whisk together until smooth. Pour the milk mixture into the flour mixture and stir until just barely combined.
Pour the soda into the batter and stir until they are no large clumps of flour, being careful not to over mix. Let the batter sit on the counter for 10 minutes to rise.
Meanwhile, heat a pan over medium heat. Prepare the pancake molds by spraying the inside with cooking spray. Place the molds on the hot pan and spoon the batter into the mold, filling no higher than halfway up the mold.
Use the back of a spoon or spatula to fill the entire mold. Let the pancake cook for 3 minutes, or until the top edges of the pancake start to pull away from the mold.
Remove the mold and flip the pancake, cooking for another 2 minutes. Remove the pancake from the pan and repeat with remaining batter. Serve warm with your choice of toppings.