Preheat oven to 350 degrees.

In a medium bowl combine flour, dark cocoa powder, salt and baking soda.

Beat butter, sugar, brown sugar and vanilla until creamy. Add eggs, one at time. Beat well after each one.

Gradually beat in flour mixture. Stir in peanut butter chips.

Bake for about 10 minutes or until outside is firm but center seems slightly soft. Cool on baking sheets for several minutes.

Remove to rack to cool.