CAKE:Separate eggs and place egg whites into a large mixing bowl and set aside; place yolks into a small bowl and set aside.
Combine flour, lemon zest, baking powder, and salt; set aside.
Melt the 3 ounces chopped white chocolate with 1/4 cup of the half n half in a small pan over very low heat, stirring constantly, until the chocolate begins to melt- immediately remove from heat and stir until smooth.
Stir remaining half-and-half into the chocolate and let cool.
Cream margarine or butter with granulated sugar on high speed until soft and fluffy.
Beat in vanilla.
Add egg yolks, one at a time, beating well after adding each.
Alternately add the flour mixture and the chocolate mixture, beating on medium-low speed after each addition, just enough to combine (don't over beat).
Beat egg whites using clean beaters on high speed until stiff peaks form (this may take some time).
Gently fold the egg whites into the batter, then spread into 2 greased and floured 8" round baking pans.
Bake in a preheated 350°F oven for 25-30 minutes or until a toothpick inserted in the center tests clean.
Let cake cool in pans on a wire rack for 10 minutes, then remove from pans and let cool completely.
In a small bowl, combine 1 cup of the berries and raspberry liqueur or extract, place covered in fridge until needed.
CURLS: Using a veggie peeler, carefully drag the peeler across the broad surface of the bar of white chocolate over sheets of wax paper- curls of peeled chocolate will fall.
Carefully arrange in a single layer in an airtight plastic container and chill (amount you make is up to you- you will want enough to completely cover the top of the cake at least).
Have ready a chilled mixing bowl and chilled beaters.
Combine 1/4 cup cream and the white chocolate in a small pan and heat over very low heat, stirring constantly, until starts to melt; remove from heat and keep stirring until smooth.
Let cool completely.
Have a small pan heating to a boil (just a few inches of water).
Combine cold water and gelatin powder in a 1-cup glass measure and let stand 2 minutes.
Place measuring cup into the boiling water (wear kitchen mitts) and heat and stir until gelatin is dissolved (or place in microwave for a few seconds until dissolved).
Using the chilled bowl and beaters, whip the remaining 1 1/4 cups cream and sugar on medium speed, while gradually drizzling in the gelatin mixture.
Beat until soft peaks form.
Continue beating, while adding the cooled chocolate mixture, this time beating until stiff peaks form- do not over beat.
Use immediately to frost cake.
TO ASSEMBLE: Place 3 large squares of wax paper onto the cake plate, overlapping edges and letting sides hang over the plate (these will be pulled out later).
Place one cake layer onto the wax paper.
Set berry mixture into a strainer over a small bowl and let juices drain.
Using a pastry brush, brush the liquid over the cake layer.
Stir jam to soften and spread over the cake layer.
Top with 1/3 of the frosting and spoon 1 cup of the berries on top.
Place remaining cake layer on top and frost top and sides of cake with remaining frosting.
Garnish with curls and gently pull out the wax paper sheets.
Cover loosely with plastic wrap and chill up to 24 hours, if needed.
Just before serving, sprinkle with remaining 1/2 cup plain berries and dust with powdered sugar.