In a medium saucepan, melt the butter or margarine and chocolate over low heat, stirring frequently. Remove from heat. Add the sugar, eggs, and vanilla. Using a wooden spoon, lightly beat just until combined (don't overbeat or brownies will rise too high, then fall). Stir together flour and baking soda; stir into chocolate mixture.
Spread batter into a greased 8x8x2 inch baking pan. Sprinkle with toffee pieces and chocolate pieces. Bake in a 350 degree F oven for 30 minutes. Cool in pan on a wire rack. Cut into bars. Makes 16 brownies.