Combine. Place erythritol (1/2 cup), almond flour (1 1/2 cups), baking powder (1/2 teaspoon), and salt (1/4 teaspoon) in a large bowl and whisk together to combine. Add melted butter (5 tablespoons), egg (1), and vanilla extract (1 teaspoon) to the bowl and stir to combine.
Chill. Shape dough into a disk, and wrap in plastic wrap. Place in the fridge for 6 hours - overnight.
Shape. Use a rolling pin to roll the dough between two sheets of parchment paper, until it's 1/4” thick. Use cookie cutters to cut into shapes. Form excess dough into a disk and place in the fridge for 20 minutes before attempting to roll/cut again. Place cookies on the prepared cookie sheet - if the cookies are too fragile to move, place them in the freezer for 10 minutes, then try again.
Prep. Preheat oven to 375 F and line 2 baking sheets with parchment paper.
Bake on the center rack in the preheated oven for 7-9 minutes, or until the edges become lightly golden. Allow cookies to cool on the baking sheet before transferring.
Icing. Place powdered erythritol (1/4 cup) in a small bowl. Add water using ¼ teaspoon increments until a paste has formed. Place into a resealable bag and cut a small hole in the tip. Decorate your cooled cookies and enjoy!