These are guaranteed to cure the back-to-school blues, at least for the moment.
Coarsely chop 2 ounces of the chocolate and put it into the top of a double boiler. Melt the chocolate over, barely simmering water, whisking to smooth. Remove from the heat and cool to room temperature. Preheat oven to 350 degrees F.
Using an electric mixer, cream the butter, peanut butter, and brown sugar until smooth and fluffy. Beat in the egg until smooth, then the vanilla. Sift the dry ingredients into a small bowl and set aside.
Blend the melted chocolate into the creamed mixture. Stir in the dry ingredients, about one-third at a time. Coarsely chop the remaining 4 ounces of chocolate and stir it into the dough.
Using floured hands, roll the dough into 1-½-inch balls and place them onto greased baking sheets. Bake for 15 to 17 minutes. When done, the tops of the cookies will be cracked and will feel soft to gentle finger pressure. Cool briefly on the sheets, then transfer to a rack to cool.