In a small bowl, whisk together the flour and sugar.

In a separate small bowl, whisk the egg whites, butter, vanilla extract and salt until combined.

Mix the dry and wet ingredients until the batter is smooth, then cover and refrigerate for 1 hour (or up to 2 days).

When ready to bake, preheat the oven to 400°F (200°C), and line a baking sheet with a silicone baking mat and set aside.

Check the consistency of the batter – it should be like a thick pancake batter.

Bake only 2 cookies at a time: for each cookie place about 2 teaspoons of batter onto the mat and using the back of a spoon, spread the dough from the center outwards in a circular fashion until you have a circle about 5-inches (12 ½ cm) wide.

Bake the cookies for 5 -6 minutes, until the edges look golden. Remove the tray from the oven and while the tuiles are on the mat and still hot, quickly roll the cookies into a cigar shape and transfer to a wire rack to cool. (You can roll by hand or use a wooden spoon handle)

Once the tuiles are completely cool, transfer to an airtight container and keep at room temperature. Tuile will stay crisp for up to one day if properly stored. After this they may soften a bit but will still be good for up to 3 days.