Like so many other cookies, this simple French cookie is made from every day ingredients; butter, sugar and flour and egg. Langues de Chat or cat's tongues in English, are sweet and thin as wafer cookies.
Mix soft butter, sugar and salt until smooth. (NOTE 2)
Add egg, vanilla extract and flour and mix again until smooth.
Transfer dough into a piping bag. Use a plain piping tip with an opening of about 1/4". Pipe out strips on baking sheet lined with parchment paper of silicone mat. Pipe out cat's tongues that are about 3" long and 2" apart. They don't have to be perfect; cat's tongues are not all the same.
Bake the cat's tongues in an oven of 350 degrees F for about 7-12 minutes. The cookies are done when they are deep brown around the edges and still have a pale golden color in the middle.
Allow the cookies to cool on a wire rack.
Notes
Instead of an entire egg, you can use 2 egg whites.