In the microwave or in a metal bowl over a pan of simmering water, melt 1 1/3 cups of the chocolate chips, and the butter stirring occasionally until smooth. Remove from heat and set aside to cool. In a large bowl, whip eggs and sugar until thick and pale, about 2 minutes. Stir in the vanilla and the chocolate mixture until well mixed. Combine the flour, cocoa, baking powder and salt; gradually stir into the chocolate mixture. Fold in miniature chocolate chips. Cover dough and chill for at least an hour or overnight.
Preheat oven to 350 degrees F (175 degrees C). Roll chilled dough into 1 inch balls. Roll in chopped walnuts and then flatten cookie dough. Place on ungreased cookie sheets so they are 2 inches apart.
Bake for 9 to 11 minutes in the preheated oven. Allow cookies to cool on baking sheet for 5 minutes before removing to a wire rack to cool completely.
Makes 36 cookies.