1 cup butter, softened

scant 3/4 cup sugar

1 egg yolk, lightly beaten

2 teaspoons vanilla extract

2 1/4 cups all purpose flour

1/4 cup unsweetened cocoa powder

8 oz bittersweet chocolate (I used bittersweet chips)

1/4 cup semi sweet chocolate chips

pinch salt

Preheat the oven to 375. Line 2 cookie sheets with parchment paper.

Put the butter and sugar into a bowl and mix them up well with a wooden spoon. Beat in the egg yolk and vanilla. Sift together the flour, cocoa, and salt. Add to mixture. Add chocolate. At this point the batter became quite thick so I just used my hands to mix everything.

I used a cookie scoop and then flattened them a bit with my fingers. Bake 12 - 15 minutes. Let cool on the cookie sheet for 5 - 10 minutes, then transfer to a wire rack to cool.