Prewarm the oven to 177ºC(350ºF), rack in the middle.
Cut 3 rectangular pieces of 13″x 9″ parchment paper.
Lightly butter 13″x 9″ baking pan and line the bottom with parchment paper.
Make double boiler of medium size saucepan and fitting stainless steel mixing bowl. Make sure the water doesn’t touch the bowl. Over medium heat bring the water to simmer in the saucepan. Whisk constantly sugar and egg yolks in the bowl placed over the saucepan and bring the mixture temperature to lukewarm or about 30ºC (86ºF).
Beat egg mixture with hand held electric mixer at high speed until mixture triples by volume, about 3-5 minutes.
In two additions sift combined flour and salt to the egg mixture and fold it in with silicone spatula.
Transfer the mixture to the baking pan and spread evenly with an offset metal spatula. Make sure the corners are filled.
Bake for 15 minutes or until the top springs back when lightly pressed in the middle, with tips of the fingers.
Cool for 3 minutes and then run knife around the edge to release the cake.
Invert the baking pan on parchment paper lined baking sheet. Gently and carefully peel off the top paper. Let it cool completely.
Let the baking pan cool off for 15-20 minutes before buttering and lining with parchment paper, in preparation to bake the second layer.
Walnut Layer
Lightly butter baking pan and line the bottom with parchment paper.
In a small mixing bowl whisk together ground walnuts, flour and salt.
Follow the same process for to warm up and beat egg and sugar mixture as for the plain layer.
In two additions add ground walnut mixture to the beaten eggs and fold it in with silicone spatula.
Transfer the mixture to the baking pan and spread evenly with an offset metal spatula. Make sure the corners are filled.
Bake for 15 minutes or until the top springs back when lightly pressed in the middle, with tips of the fingers.
Cool for 3 minutes and then run knife around the edge to release the cake.
Invert the baking pan on parchment paper lined baking sheet. Gently and carefully peel off the top paper. Let it cool completely.
Let the baking pan cool off for 15-20 minutes before buttering and lining with parchment paper, in preparation to bake the third layer.
Cocoa Layer
Lightly butter baking pan and line the bottom with parchment paper.
In a small mixing bowl sift and mix together cocoa, flour and salt.
Follow the same process for to warm up and beat egg and sugar mixture as for previous two layers.
In two additions add cocoa mixture to the beaten eggs and fold it in with silicone spatula.
Transfer the mixture to the baking pan and spread evenly with an offset metal spatula. Make sure the corners are filled.
Bake for 15 minutes or until the top springs back when lightly pressed in the middle, with tips of the fingers.
Cool for 3 minutes and then run knife around the edge to release the cake.
Invert the baking pan on parchment paper lined baking sheet. Gently and carefully peel off the top paper. Let it cool completely.
Rum Syrup
In a small saucepan stir together sugar, water, orange zest strip and lemon zest strip. Stir over medium heat until boiling. Let boil for 5 minutes, without stirring. Take off heat and let cool completely.
Remove orange and lemon zest, stir in the rum.
Pastry Cream
In a medium size saucepan add 3 cups of milk and bring to simmer over medium heat.
Add 1 cup of milk to another medium size heavy bottom saucepan. Sprinkle the cornstarch over the cold milk, whisk until dissolved. Whisk in the sugar and egg yolks.
Place the sauce pan with cold yolk mixture over medium heat.
Whisking constantly gradually add in the hot milk.
Continue cooking over medium heat until the mixture comes to full boil, whisk continuously. This will take about 15-20 minutes.
Remove from heat and stir in vanilla extract.
Transfer the hot mixture to a medium size mixing bowl. Set this bowl into a larger bowl filled with the cold water and ice.
Stir frequently and let the pastry cream cool to room temperature.
Assembly
In a small mixing bowl mix together raisins and walnuts.
In a small saucepan bring apricot preserves to boil, stir frequently. Take it off the heat, but keep it warm.
Clean, dry and use the same 13″x 9″ baking pan for the cake assembly.
Place the walnut layer on the bottom of the pan.
Measure and brush the walnut layer with 1/3 of Rum Syrup.
Spread evenly warm apricot preserves covering the whole layer.
Measure and spread evenly 1/3 of pastry cream, use an offset spatula to level off.
Sprinkle with 1/2 of walnut/raisin mixture across the whole layer.
Carefully install the second layer or Cocoa Layer.
Measure and brush the cocoa layer with 1/2 of the remaining Rum Syrup.
Measure and spread evenly 1/2 of the remaining pastry cream, use an offset spatula to level off.
Sprinkle with remaining walnut/raisin mixture across the whole layer.
Carefully install the third layer or Plain Layer.
Brush the plain layer with the remaining Rum Syrup.
Spread evenly the remaining pastry cream, use an offset spatula to level off.
Sift cocoa over the top.
Cover tightly with plastic wrap and refrigerate overnight.
Sweetened Whipped Cream
Add chilled cream, confectioner’s sugar and vanilla extract to a chilled medium size mixing bowl. Using a hand held electrical mixer beat to stiff peaks.
Rum Chocolate Sauce
In a medium size heavy bottomed saucepan stir together sugar, water, rum and chocolate. Bring to boil over medium heat, whisk constantly. Let it cool off.
Note: Chocolate sauce is kept refrigerated. Warm up, just until heated thru (not boiled!).
Serving
Use 2″ ice cream scoop or large dessert spoon to scoop 2-3 dumplings from the assembled cake. The dumplings should be arranged in a bowl or on a plate.
Use a pastry bag and 9/16″ open star tip to pipe rosettes on the top.
Drizzle with rum chocolate sauce and serve chilled.