In a medium mixing bowl, whisk together the flour, baking powder, baking soda, and salt.
In another bowl, whisk together the melted butter, the milk, the vinegar, the sugar, and the vanilla.
Pour the wet ingredients into the dry ingredients and whisk together until combined. Don't overmix. It's OK if there are a few small lumps.
Put the batter in a squeeze bottle or piping bag.
Heat a non-stick frying pan over medium-low heat (there's no need to grease the pan if it's non-stick).
Steadily hold the bottle upright and squeeze small blobs, about 1-2 inches in diameter (2.5-5 cm). I fit about 7 pancakes in a pan. Try and work as fast as you can, so you can make them all the same size.
As soon as you see pockets of bubbles on the surface, flip them over. This will take about 2 minutes.
When you flip them over, cook the pancakes for another 15-20 seconds. Don't overcook them or they'll get dry and could burn.