Coat a 13 by 9 by 2-inch baking pan with nonstick cooking spray.
Melt together butter and chocolate in bowl set over simmering water in saucepan. Stir until smooth. Set aside to cool.
Beat eggs and sugar in large bowl until well combined, about 1 minute. Beat in vanilla, 1 tablespoon liqueur and the salt. Stir in flour in 3 additions. Fold in walnuts and chocolate chips. Spread half of batter over bottom of prepared pan.
Mix together preserves and remaining liqueur in small bowl. Spread over batter in pan. Place in freezer for about for about 20 minutes or until preserves are set. Spread remaining batter over top of preserves.
Bake for 45 minutes or until wooden pick inserted in center comes out clean. Cool in pan on wire rack 15 minutes. Cut into 32 brownies. Let cool completely.
To serve, dust with confectioners' sugar, if desired.