Begin by putting the egg whites in a large bowl and mixing them with a pinch of salt until white and fluffy.
Gradually add the sugar, mixing continuously until fully dissolved and stiff peaks form. You will know the meringue is ready when you turn the bowl upside down and the mixture doesn't move.
Incorporate the ground walnuts, mixing them in with a spatula, always using upward movements to maintain the fluffiness of the egg whites. Do the same with the flour.
Preheat your oven to 180 ℃/ 356℉.
If you have good dexterity with cutting even sponge cake layers you can place all the batter in a single tray and bake it all in one go. But just to be safe, we recommend dividing the batter equally into 3 different bowls and bake each layer individually.
Line a baking tray with parchment paper and pour in the contents of the 1st bowl, spreading it evenly with a spatula.
Place in the oven and bake for about 15 minutes, until the edges become golden brown. Repeat the process for the remaining 2 bowls of batter. Set them aside until completely cooled.
How to Make the Cream:
To make the cream, add water to a large pot and prepare a smaller pot or heat-proof that can me placed inside to form a bain-marie. There should be about 2 cm/ about 1 inch distance between the bottom of the smaller bowl/pot and the level of the water in the bigger pot.
Bring the water in the large pot to a boil on medium heat and reduce to a simmer, place over the larger pot and mix the egg yolks and sugar and stir continuously until the mixture thickens and becomes glossy, like a glaze.
When the cream reaches this creamy consistency, take it off the heat, add the vanilla extract and allow it to cool.
How to Make the “Krantz” (Caramelized Walnuts):
Heat up a pan over medium heat and add the sugar. Stirring continuously, melt the sugar until it turns into caramel, making sure not to burn it.
Once the sugar has fully melted, add the chopped walnuts and stir, coating the pieces well. Transfer the caramelized walnuts onto parchment paper and let it cool completely.
Crush the caramelized walnut pieces using a rolling pin and set aside.
How to Assemble Krantz Cake:
Mix the cake cream with 10 ⅔ oz/ 300g of soft butter until well-combined. Divide it into 3 parts: 2 larger for filling in between the sponge cake layers, and reserve 1 smaller part to spread on top of the cake.
Place the first cake layer down on your platter/tray of your choice and add the first third of the cream (about 1/2 an inch thick layer). Top with the second sponge layer and another third of cream on top.
Finally, place the 3rd sponge sheet and cover with cream, spreading it evenly with the side of a knife.
Sprinkle the top with “Krantz” (the caramelized walnuts) and refrigerate for at least 2-3 hours until the cream becomes firm.