Melt unsweetened chocolate and margarine in saucepan over low heat. Add liquid sweetener, vanilla and beaten eggs. Stir until well blended. Stir in chopped walnuts. Pour into a greased 8x8 pan. Level in pan. Bake in slow oven at 325 for 20 minutes. Cool and cut into bars. Makes 32 cookie bars, each contains 55 calories. 2 bars = 1 1/4 bread exchange and 2 fat exchange.