Separate the yolks and the whites into two medium bowls, being careful not to drop any yolk into the egg whites.

Whisk together egg yolks, salt, and sugar until lightly thickened - about 45 seconds.

Add half the milk and flour and stir until batter is smooth. Repeat with the remaining flour and milk, this time also adding the butter and vanilla. Stir just until it is mixed through.

Using a handheld mixer, beat egg whites until they quadruple in size and form soft peaks. For me, this took about four minutes.

Using a rubber spatula, very gently fold egg whites into batter. You want to be gentle and avoid stirring or mixing too much. Fold until just incorporated, the batter will still be lumpy.

Set a nonstick pan over low to medium-low heat. Heat pan for 2-3 minutes until a drop of water skids across the pan before evaporating. Do NOT add any butter or oil to pan - it's not needed and might overcook the pancakes.

Using a tablespoon, drop heaping spoons of batter into the pan. Cook until the pancakes rise, and then flip over using a rubber spatula and continue cooking. Depending on your stove, you may need to adjust the heat. You want them to cook low and slow, so the custard in the middle sets, without the bottoms of the pancake getting too dark. For my stove, it works out to be about a minute to a 90 seconds on each side.