Preheat your oven to 350F. Line two baking sheets or cookie trays with parchment paper and set aside (see notes).
In a large bowl using an electric hand mixer or using a stand mixer fitted with the paddle attachment, beat ½ cup butter on medium-high speed until soft and creamy (2-3 minutes).
Add ½ cup sugar and continue beating until light and fluffy (4-5 minutes). Remember to scrape the bottom and sides of your mixing bowl.
Add 1 tsp vanilla extract and egg whites and beat until incorporated (4-5 minutes).
Switch to low speed and gradually add 1 cup flour and a pinch of salt until combined.
Transfer the cookie dough into a piping bag or a Ziploc bag with one of the tips cut to about 1/2 inch in diameter.
Pipe 3-inch long cookies on your prepared baking pans, allowing about an inch of space around each cookie.
Bake the lengua de gato for 12-15 minutes or until they’re dry in the middle and starting to turn a light brown on the edges.
Remove the pans from the oven and allow the cookies to slightly cool in the pan. After a few minutes, slide the parchment paper into a cooling rack to allow the lengua de gato to cool completely. Carefully peel cookies from the parchment paper and enjoy!
Total number of cookies depend on how big/long you pipe your cookie dough. I usually get at least 60 cookies from this recipe.