Measure all wet ingredients (i.e., eggs, milk, vanilla, and butter) and allow to come to room temperature.
Next, whisk the flour, salt, baking powder, and sugar together in a medium bowl and set aside.
Beat the eggs, milk, and vanilla at high speed for 3 minutes in a stand mixer (or a large bowl if using a hand mixer). The mixture should increase in volume and be foamy. Decrease the speed to “stir” (i.e., the lowest speed on the mixer) and add the butter. The mixture will deflate slightly.
Quickly and carefully add the dry ingredients. Try to avoid losing all of the air you previously beat into the batter. It’s ok if there are a few lumps left in the batter after mixing. It is better to have a few lumps than to overmix the batter. Leave the batter to sit while the pan/griddle is heating up. It will thicken while it rests.