Preheat the oven to 375°F (190°C). Line a baking sheet with baking parchment paper or a silicone mat.
Add the butter and granulated sugar to a medium bowl and cream by beating with an electric mixer until pale and fluffy.
Beat in the egg yolks.
Sift in the flour and powdered icing sugar and stir by hand to form a stiff dough.
Lightly flour the work surface and roll the sable dough out to ¼” thick. Cut out cookies with a round (or other shape) cookie cutter (I use a 2” cookie cutter). Roll out the dough scraps and repeat until it’s all used up.
Place the cookies onto the tray (use 2 trays if necessary), leaving room between the cookies, and place into the fridge to chill for 15 minutes.
Bake the sable cookies for 12 minutes, or until they're golden brown. Transfer the cookies to a wire cooling rack to cool completely.
Notes
Before making the dough, leave out the butter and eggs to come to room temperature first. This will help ensure the texture says intact when baked.
Don’t overwork the dough. Mix the cookie dough just until combined. Overworking flour could cause the dough to stiffen up compromising the texture of the cookie.
When adding the cookie shapes to the baking sheet, you may need to use two baking sheets depending on their size.
The cookies should be completely cool before serving. Once cool, the texture of the cookie will be a classic shortbread.