Preheat oven to 350 degree F. Grease and lightly flour two 9x1-1/2-inch round baking pans; set aside. Stir together flour, baking powder, baking soda, and salt in a mixing bowl; set aside.
Beat butter in a large mixing bowl with an electric mixer on medium to high speed for 30 seconds. Add sugar; beat until well-mixed. Add eggs, one at a time, beating well after each addition. Beat in chocolate and vanilla. Add the dry mixture and the water alternately to beaten mixture, beating on low speed after each addition, just until combined. Pour batter into the prepared pans; spread evenly.
Bake in the preheated oven for 30 to 35 minutes or until a wooden toothpick inserted near centers comes out clean. Cool cake layers in pans on wire racks for 10 minutes. Remove cakes from pans. Cool cake layers thoroughly on racks.
Place one cake layer, cut side up, on serving plate; spread with half of the raspberry jam. Top with second cake layer, cut side down. Spread with about 2/3 cup Raspberry-Chocolate Frosting.
Place another cake layer, cut side up, on top of frosting; spread with remaining jam. Top with last cake layer, cut side down.
Frost top and sides with all but 3/4 cup of the remaining frosting. Pipe remaining frosting on top of cake. If desired, garnish with raspberries. Makes 14 servings.
Impress your friends and family with this 4-layer decadent dessert at your next holiday gathering.