Preheat oven to 160°C.

Cream the butter, salt and sugar using electric mixer. Continue mixing for about 2 minutes or until light and fluffy.

While mixing, gradually add the egg whites followed by vanilla extract. Mix for a minute at medium-low speed

Turn speed to low and gradually add the flour while continuously mixing. Continue to mix until the ingredients are well incorporated and the batter becomes smooth.

Get a piping bag with a star or round tip (#21) or just cut the tip of the bag to make a hole. Spoon the mixture into the piping bag.

On a baking tray lined with parchment paper or silicon mat, pipe round, thin strips of batter about 3-inches long per piece. Space them out about 2 inch apart so they have space to spread while baking.

Bake for 10-12 minutes or until edges start to turn golden.

Remove from the oven and loosen cookies from the trays while still warm. When completely cool, pack them in airtight containers.