CAKE LAYER: Heat oven 350 degrees. Grease an 28 cm X 43 cm baking pan. In food processor or with eledtric mixer, process or beat the butter, flour, sugar and salt until mixture holds together and forms a dough. Press over bottom of pan. Bake 20 minutes or until light golden and firm when touched. BROWNIE LAYER: Heat butter and chocolate in a small saucepan over low heat, stirring often, until melted. Cook 5 minutes. In a medium-size bowl, whisk eggs, sugar, flour and baking powder until blended. Whisk in cooled chocolate mixture. Pour over shortbread base. Bake 20 minutes or until top feels firm. Cool in pan before cutting in bars. Food Exchanges per serving: 1 STARCH/BREAD EXCHANGE + -20ºC RUIT EXCHANGE + -10ºC AT EXCHANGE; CAL: 148; PRO: 2g; CAR: 10g; CHO WITH BUTTER: 38g; CHO WITH MARGARINE: 18g; SOD: 94mg;