Here's what you will need to make it:
- 1 and 2/3 sticks butter, softened
- 1 cup sugar
- 1 egg
- 1 teaspoon vanilla
- 2 cups flour
- 1/2 teaspoon salt
- 1/4 cup cocoa powder
Here's what you have to do:
1. Check with a grown-up before you start this.
2. Cream butter and sugar together until pale and fluffy. You cream butter by putting a softened stick of butter in a bowl and mashing it with the back of a spoon until it's creamy.
3. Beat in an egg and vanilla extract.
4. Mix together flour and salt.
5. Stir the flour gradually into the creamed mixture.
6. When the dough becomes too stiff to stir, mix in the remaining flour by hand.
7. Divide the dough in half and add cocoa powder to one half.
8. Gather the dough into balls, wrap in plastic wrap and refrigerate for about an hour before rolling.
9. When thoroughly chilled, roll the plain dough on a lightly floured surface into a rectangle about 1/4 inch thick.
10. Do the same with the chocolate dough.
11. Carefully lay the chocolate dough on top of the plain one and roll lightly with your rolling pin to seal them.
12. Trim the edges of the dough with a knife.
13. Roll up the doughs the long way and wrap the cylinder in plastic wrap and refrigerate for about 2 hours.
14. When the dough is hard, unwrap it, and slice it into rounds.
15. Bake the slices on a greased cookie sheet in a preheated 375 degree oven until firm -- about 10 minutes.
16. Remove from the oven and transfer the cookies to a wire rack to cool.