Combine the graham cracker crumbs, sugar, cocoa powder and butter until well blended. Press even amounts of the mixture onto the bottoms of lightly buttered mini muffin tins. Melt one cup of the chips and set aside to cool. In a mixer, beat the cheese until fluffy. Gradually beat in the condensed milk and melted chocolate and stir until smooth. Add the eggs and vanilla and mix in thoroughly. Spoon the batter into the prepared cups. Top with remaining chips. Bake in preheated 300 degree oven for about 15 to 20 minutes or until set. Let cool and refrigerate. Recipe from Rita Bellantoni of Norwalk, CT. ----