Preheat the oven to 350F (177C) convection and line two large cookie sheets with parchment paper.
Place the egg whites in the bowl of the stand mixer and using the whisk attachment, at full speed, beat until they're frothy.
6 large eggs (50-60 grams each)
With the mixer on medium speed, stream in the cup of sugar. Turn the mixer up to full speed and beat just until the meringue reaches stiff peaks.
150 grams (3/4 cup) granulated sugar
Add in the egg yolks and vanilla and turn the mixer to medium-high speed, mixing, a few seconds, just until they're fully combined.
1 teaspoons vanilla extract, 6 large eggs (50-60 grams each)
Sift in the flour and salt and turn the mixer up to medium-low speed, mixing just until the flour is incorporated.
240 grams (2 cups) all-purpose flour, 1/4 teaspoon fine sea salt
Use the rubber spatula to gently scrape the bottom and edge of the bowl and make sure it's all combined.
Gently place the batter in a large piping bag fit with a large round tip and pipe identical lines of batter (just like eclairs). Try to let the piping bag glide and not press down as your piping so you don't deflate the air.
Sprinkle the cookies with granulated sugar (I do a generous amount because a lot of it falls off).
granulated sugar
Bake on the middle rack (top rack if not convection) for 12ish minutes (rotate after 8-9 minutes if one side is getting darker) until they're dry and lightly golden brown.