Combine first 9 ingredients; beat at medium speed of an electric mixer 2 minutes. Stir in water. Pour batter into 2 greased and floured 8-inch round cakepans. Bake at 350° for 25 minutes or until a wooden pick inserted in center comes out clean. Cool in pans on wire racks 10 minutes; remove from pans. Let cool.
Combine melted chocolate and raspberry nectar. Let cool. Beat butter at medium speed of electric mixer until fluffy. Add 2 tablespoons powdered sugar; beat until blended. Add chocolate mixture, beating well. Fold whipped cream into chocolate mixture.
Stir preserves well. Slice each cake layer in half horizontally. Place 1 layer on plate; spread with 1/4 cup preserves. Spread one-third of chocolate mixture over preserves. Repeat with next 2 layers and remaining preserves and chocolate mixture. Top with fourth layer.
Beat 2 cups whipping cream until foamy; add 1/3 cup powdered sugar, beating until soft peaks form. Spread on sides and pipe on top of cake.