In a saucepan over low heat, melt butter and bittersweet chocolate; cool slightly. In a bowl, beat eggs, sugar and vanilla. Stir in chocolate mixture. Gradually add flour until blended. Stir in chips and walnuts. Spread into a greased 13X9X2 in baking pan. Bake at 350° for 30-35 minutes or until a toothpick inserted near the center comes out clean. Do not overbake. Cool on a wire rack.
In a small saucepan, combine white chocolate and creamer. Cook and stir over low heat until smooth; remove from heat. Refrigerate for 30-40 minutes or until chilled. In a mixing bowl, beat cream until soft peaks form; fold into white chocolate mixture. Beat on medium speed until stiff peaks form, about 4 minutes. Fold in chopped candies. Spread over brownies. Cover and refrigerate.
In a small saucepan, combine bittersweet chocolate and cream. Cook and stir over low heat until chocolate is melted and smooth; remove from heat and stir in butter until melted. Cool to room temperature. Carefully spread over filling. Cover and refrigerated for 1 hour or until icing is set. Cut into bars. Garnish with additional candies if desired. Store in refrigerator.