In a bowl over a pan of simmering water (or in the microwave) melt the chocolate and remove from heat. In a separate bowl sift the flour and salt together.
Using an electric mixer, beat the butter until creamy. Add sugar and beat until light and fluffy, about 2 minutes. Beat in the eggs and vanilla. Gradually beat in the melted chocolate, then the flour and peanuts.
Wrap the dough with plastic wrap and refrigerate until firm, about 2 hours. It will be easier if you shape it into a log shape. Preheat oven to 180 degrees C.
Grease 2 baking trays. Cut slices of the dough and place 3cm apart on the trays. Bake 10 minutes. Cool on wire racks.