• Preheat oven to 325 ℉. Line a baking sheet with parchment paper or a silicone baking mat. Set aside.
• In a large bowl using a hand held mixer, or a standing mixer with a beater attachment, cream the softened butter and granulated sugar until light and creamy, about 2-3 minutes.
• Mix in the egg yolk, salt, and vanilla extract.
• Add the flour and mix until just combined. Do not overmix the cookie dough.
• Using an ice cream scoop or a large spoon, scoop about about 1.5 tablespoon balls of dough and roll in your hands until a uniform ball forms.
• If desired, roll the ball in more granulated sugar.
• Place the balls of dough on the prepared baking sheet, keeping them about 2 inches apart. Using your thumb, finger, or the back of a 1/2 teaspoon, gently press down in the middle of the ball of cookie dough.
• If the dough cracks, gently press the cookie it back together with your fingers.
• Bake in the preheated oven until the cookies just start to brown, about 12-15 minutes.
• Remove the cookies from the oven and cool on the baking sheet for 5-10 minutes. Then remove the cookies by placing on a cooling rack to cool completely before filling.

Icing

• In a medium bow, mix the powdered sugar, milk, extracts, and any optional food coloring until well combined.
• Add to a pastry bag or a ziplock back with the tip cut off. Fill the completely cooled cookies with the icing. If desired let the icing harden a bit and then enjoy!