Pre-heat the oven to 180°C / 360°F.
Beat the egg yolks and half the sugar (½ cup) in a large mixing bowl until thick and pale (around 1-2 mins).
6 eggs, 1 cup caster sugar
Next, fold through the self raising flour, salt and ground walnuts, then add in the vanilla essence.
1 cup self raising flour, 3 cups walnuts, 1 pinch salt, 1 tsp vanilla essence
In a separate large mixing bowl, whisk the egg whites until soft peaks form, then whisk in the remaining sugar (½ cup), pouring in a little at a time. It should become thick and glossy like a meringue / pavlova base.
6 eggs, 1 cup caster sugar
Add one - two scoops of the beaten egg whites to the walnut mixture, mixing it through until well combined. Note: It may be a little tough to start, but will loosen up as it blends into the mixture. Pour in the remaining egg whites and fold through the cake mix.
Pour the cake mix into a lined (or greased) 29cm rectangle baking dish and bake for 40 minutes until golden and firm to touch. Test with a wooden skewer that the middle is cooked through.
Remove the cake from the oven and skewer the top all over to help the syrup soak in. Carefully pour a couple of scoops of the syrup over the entire top of the cake while it’s nice and hot.
Once coated, and the syrup has been absorbed, pour another couple of scoops over and allow to soak in again. Repeat until all the syrup is soaked in. If there are any areas holding too liquid on top, you can skewer these to help the syrup soak through.
Allow to cool, then slice and serve. To cut, slice into vertically into strips, then diagonally to make diamond shapes. See below for the shaping. Serve by itself, or top with more crushed walnuts, icing sugar, whipped cream or ice-cream.