Rocky Road Sandwich Cookies

FOR THE COOKIES:
Stir chocolate in a small, heavy saucepan over low heat until melted. Set aside. Using electric mixer, beat the butter in a large bowl until fluffy. Beat in the sugar and baking powder. Beat in the melted chocolate, egg, and vanilla. Beat in as much of the flour as you can with the mixer. Stir in any remaining flour with a wooden spoon. Shape dough into two 7-inch-long logs. Wrap with plastic. Chill dough until firm, about 2 hours.

Preheat oven to 375 degrees F.

Cut dough logs crosswise into 1/4-inch-thick slices. Place slices 2 inches apart on cookie sheets. Bake until edges of cookies are firm and bottoms are lightly browned, about 10 minutes. Transfer cookies to a rack and cool.

FOR THE FILLING:
Using an electric mixer, beat cream cheese and marshmallow cream in large bowl until well blended. Stir in walnuts, pecans, or peanuts. Spread about 2 teaspoons of the filling over bottoms of half of the cookies; top with remaining cookies to form sandwiches.

FOR THE CHOCOLATE DRIZZLE:
Stir chocolate and shortening in a small, heavy saucepan over low heat until melted. Drizzle chocolate mixture over tops of cookies. Cover and refrigerate.