1. Preheat oven to 170℃ (340F) degree. Combine eggwhites and sugar well in a bowl. Add melted butter, vanilla, salt, coffee powder (optional) and sifted flour. Mix well with a whisk until smooth in texture.
2. Add the flaked almonds and mix to combine evenly with a spatula.
3. Spread the mixture evenly using your wet finger on the prepared sheets of an oven tray ( parchment paper or baking paper works too). Alternatively you can spoon a tablespoon of the almond mixture and spread into a circle thinly using your wet a finger.
4. Bake at 170C degree for about 10~12 mins or until lightly golden.
5. Remove from the oven and let it cool to room temperature. Break the tuile as you desire.