Trace a 10″ circle onto 5 sheets of parchment paper and set aside.
Preheat the oven to 325F.
With an electric mixer beat the egg whites while gradually adding the sugar for about 5 minutes, or until stiff.
Turn the mixer to the lowest speed and add in the vanilla, walnuts and flour until just combined.
Divide the batter equally into 5 bowls.
Take a baking sheet, turn it upside down, and place a piece of parchment paper on top (turn the parchment paper upside down, too, so your circle marking is underneath and not actually touching the batter).
Evenly spread the batter inside the circle.
Bake for 14 minutes, until just starting to turn golden brown. They should still look kind of soft but should not feel sticky when touched. Place on a wire rack to cool.
Take a second baking sheet and repeat the process (you always want to make sure that you place the batter on a cool baking sheet) until you have 5 layers. Cool completely.
Walnut Cream Filling:
In a medium bowl beat the egg whites and sugar together for about 30 seconds.
Prepare a double broiler by filling the lower pot with 2″ of water and bring to a slow boil.
Place the egg yolks and sugar into the top portion of the double broiler and cook, stirring frequently, for 15 minutes.
Allow to cool.
In a medium bowl, beat the butter until light and fluffy (about 2 minutes).
With an electric mixer, beat the cooled egg yolks for 30 seconds, and then incorporate into the soft butter.
Add in the ground walnuts and mix until just combined.
Set aside 2 TBSP of this for the end.
Divide the remaining filling into 4 bowls.
Line a large tray with some parchment paper.
Remove one cake layer from its parchment paper and lay on the baking tray.
Evenly spread one quantity of filling over top.
Place another cake layer on top of the filling, and repeat until the last cake layer is laid on the top. The last layer should be placed upside down to help get a flat surface on the top of the cake.
Place a piece of parchment paper on the top of the torte.
Place another baking sheet on top of the torte, and place something heavy (like a pot with some water in it) on top to help weight the torte down.
Place in the fridge for 1 hour.
Apricot Jam Glaze:
In a small saucepan, heat the apricot jam and water together until just warm.
Remove the torte from the fridge, and remove the pot and parchment paper as well.
Spread a very thin layer of the jam on the top of the torte.
Place back in the fridge for 30 minutes to set.
In a microwave, heat together the chocolate and oil in ten second intervals, and stir until melted.
Place in a piping bag or a ziplock with the corner cut off.
In a medium bowl, mix (by hand) the powdered sugar, oil, and lemon juice.
Add the hot water a TBSP at a time until the mixture is creamy (not runny!) and mix vigorously for a few minutes.
With a hot wet knife, quickly spread the icing over the apricot layer.
Note: You will probably have some extra icing, which is fine. Its better to have more than not enough, so just use as much as you need to cover the top of the cake only.
With the chocolate, draw 4 concentric circles on the top of the cake.
With a toothpick, draw 6 lines through the circles (each line starting in the center and fanning out to the edge).
Allow the cake to rest in the fridge for at least 24 hours before slicing.
Covered with a cake dome, this cake will last up to 7 days in the fridge.