Cocoa Sables

1 . Stage

Mix flour, cocoa powder, and salt in a bowl and set aside.

2 . Stage

Beat softened butter and sugar together with an electric mixer until the mixture looks like overwhipped whipped cream. Add egg yolk and vanilla extract; mix well. Add dry ingredients. Use a spatula to mix them in until evenly moistened.

3 . Stage

Divide the dough into thirds or quarters and knead a little bit on a large sheet of waxed paper. Gather into a ball, then shape into a 1 1/2-inch cylinder or square tube. Wrap up with the waxed paper, pushing in the sides so that the tube is evenly thick from left to right. Repeat with remaining dough.

4 . Stage

Refrigerate dough for at least 1 hour, and up to overnight.

5 . Stage

Preheat the oven to 350 degrees F (175 degrees C). Line baking sheets with parchment paper.

6 . Stage

Slice dough into 1/4-inch thick cookies with a sharp knife. Arrange on the baking sheets, spacing them 1/2 inch apart.

7 . Stage

Bake in the preheated oven until firm, 20 to 25 minutes. Cool completely before eating.