White and Bittersweet Chocolate Chunk Bars

Heat oven to 350 °F. Lightly grease a 9-inch square pan. Melt butter in a small saucepan. Remove from heat and add half the white chocolate. Set aside while chocolate melts. Beat eggs in a large bowl with an electric mixer until frothy. Gradually add sugar and beat until mixture is pale, about 3 minutes. Beat in vanilla. In a small bowl, mix 2 tablespoons of the flour with the walnuts and raisins. Stir butter mixture and remaining flour into beaten eggs until blended. Stir in raisin mixture, remaining white chocolate and the bittersweet chocolate. Spread in prepared pan. Bake 30 minutes or until edges begin to pull away slightly from sides of pan. Cool in pan on wire rack at least 3 hours before cutting in bars.