Adjust two racks to divide the oven into thirds. Preheat the oven to 350 degrees. Have ready two ungreased baking sheets.
In a food processor fitted with a steel blade, process the walnuts with 2 tablespoons of the confectioners' sugar until finely ground.
In a medium-size bowl, with a whisk, combine the flour and 3/4 cup of the ground-walnut mixture until thoroughly mixed.
In a large bowl, with an electric mixer at medium-high speed, beat together the butter, the remaining confectioners' sugar, and vanilla until creamy, 2 to 3 minutes. With the mixer at medium-low speed, gradually add the flour mixture, beating just until blended. Scoop heaping measuring teaspoonfuls of the dough out of the bowl and roll them into 1-inch balls between the palms of your hands. Arrange the balls on the baking sheets, spacing them about 2 inches apart. Bake for about 11 minutes until golden around the edges. Reverse the baking sheets on the racks and from front to back once during baking. With a wide turner, immediately transfer the cookies to wire racks to cool completely.While the cookies are cooling, make the filling. In a medium-size saucepan set over low heat, melt together the chocolate, butter, and cream, stirring constantly until smooth. Remove from the heat and set aside to cool slightly. Stir in the vanilla until blended. Gradually add the confectioners' sugar, beating until smooth.
Sprinkle the remaining walnut mixture on a sheet of waxed paper. When the cookies have cooled, spread the bottom side of each one with a generous teaspoon of the filling. Top with the remaining cookies, flat sides down on the filling. Roll the chocolate edges of the cookies into the walnut mixture. Store in a tightly covered container, separating the layers with sheets of waxed paper.
Recipe courtesy of Gourmet Magazine