In a mixing bowl, add the butter, vanilla powder, and icing sugar. Whip the mixture to a creamy and fluffy consistency. Slowly add the egg whites and the whole egg to the mixture and continue mixing until fully combined. Then slowly add the flour and mix well until fluffy and uniform in texture.
Place the mixture into a piping bag and squeeze out approximately 2 1/2-inch/6 cm long strips (about 2 1/2-inch/6 cm apart) onto a greased baking sheet. Strips will flatten and expand in the oven into the shape of a 'cat's tongue'. Bake for approximately 6 minutes, or until golden.