Preheat over to 300. In double broiler, melt semi-sweet chocolate, set aside to cool to room temperature, in small bowl mix flour, baking soda and salt.
In medium bowl, mix brown and granulated sugar, then add butter and beat until well combined. Add the peanut butter and beat until smooth. Add eggs and vanilla and beat until combined. Add flour mixture and the milk chocolate chips and beat until no streaks are visible.
Pour in the melted chocolate and mix partial with wooden spoon until marbled. Drop dough in tablespoon mounds about 2 inches apart on ungreased baking sheet. Top cookie with whole peanut.
Bake for about 20-25 minutes until set, but still soft. Cool on the cookie sheet four about a minute then transfer to wire rack to cool completely.