Place chocolate in 2-cup glass measure. Heat uncovered, at High (600-700 Watts) for 1 minute 30 seconds or until melted. Cream butter and sugar until light. Beat in egg. Stir in breadcrumbs, vanilla, and melted chocolate. Line a 12″ round platter. Cook, uncovered, at High for 3-4 minutes, until firm. Remove from oven, stand for 2 minutes. Gently turn cookies out onto a clean surface. Cut out cookies, using a 2″ round cookie cutter, it makes 19 pieces. Arrange 9 pieces of cookies on microwave rack and bake at High for 142 minutes, remove cookies to cooking rack, leave to cool. Sandwich two cookies together with White Mountain Frosting or butter cream as filling.