• Preheat oven to 350 degrees. Line a baking sheet with parchment. Set aside.
• Beat butter and sugar until light and fluffy. Mix in egg yolk and vanilla until smooth. Add flour, baking powder and salt all at once and mix to combine.

TIP: Dough will look crumbly at first, that's normal!  Keep mixing, for longer than you think you need to and it will come together.  When everything is well incorporated, you can use clean hands to pull it all together.

• Form dough into one large ball and sprinkle 2 tablespoons sugar over it. Roll to coat.
• Place dough ball on prepared baking sheet and gently press to 7" in diameter.  Smooth edges with hands so here are no craggily edges that can get overcooked. If your hands melted the sugar into the dough, sprinkle a little extra on top.  Bake for 12-15 minutes, or until set on the edges and slightly soft in the middle.
• Note:  All ovens cook differently and baking time can vary depending on how you pressed your cookie down so set your timer but keep an eye on it and go by look over time!

Tip: If your edges are getting browned, it's probably been in there too long!

• Remove from oven and let cool completely.
• While cooling, mix up all frosting ingredients until light and fluffy. Add as much liquid as you need (a tiny bit at a time) until it is the consistency you like.
• When cookie is completely cool, frost and decorate if desired!