Set your butter out at least 30 minutes before you start to bake to let it soften. Preheat oven to 350 F. Place the wet ingredients in a mixer and mix until they are creamy. If you use stand mixer, use paddle attachment
Place the dry ingredients into another mixing bowl and stir to mix. Gradually add this mixture to the butter and mix until combined. The mixture will be crumbly
Shape the dough:
Line your sheet pan with one parchment paper, or you can lightly grease the pan if you don't use parchment paper. Spread the crumbly dough on top and cover with another sheet of parchment paper. Use a small rolling pin to press the dough and spread it evenly into the pan
Beat the egg whites with one tablespoon of water until frothy. Brush this on top of the pressed dough. You may not need all of egg white
Decorate and bake:
Sprinkle with the sliced almond and coarse sugar all over. Place the baking sheet into the oven, 3rd rack from the top and bake for about 20 minutes (25 minutes on my oven) until lightly golden brown
Cutting and cooling:
Remove from the oven once the cookie is done. Let it rest in the baking sheet for 5 minutes. Use a sharp knife to cut the cookies into shape immediately after that, do not move to cooling rack yet. I cut into diamond shapes, but you can cut into rectangle strips, squares, etc. Do this while the cookies are still warm or they will break when you try to cut them when they have cooled down
You can continue to let them cool down on the pan for another 10 minutes and they will start to crisp up and you can transfer to cooling rack to let them cool down completely
Storing:
They can be stored at room temperature in an air-tight container or jars for up to one week (it's hard to keep them for that long at our house LOL!)