Beat the egg whites until stiff and fold in half (1/4 cup) powdered sugar.
Combine the remaining sugar, nuts and cornstarch, then fold this into the stiff egg whites.
Bake two layers from the mixture, using a spring form. at 350F for 10-15 minutes. (I trace 2 circles on parchment using the 9 or 8” spring form Place the parchment on a baking sheet Then I divide the batter between the 2 circles and lightly smooth to the lines of the circle then bake at 350 for 10 to 15 minutes. This is like a large macaroon and should be dry when done.
In a large bowl beat the egg yolks with 3 Tbsp warm water until creamy then add ¼ cup of powered sugar.
In a medium bowl beat the egg whites with the remaining ¼ cup sugar until stiff.
Fold the egg whites into the yolks and add the flour, cornstarch, baking powder and lemon zest to make a batter.
Using the same sized spring form as for the nut layer, grease or line with parchment then add batter.
Bake for 20 minutes at 350°F.
Beat the butter until creamy.
Add the sugar and egg yolk and lastly the Kirsch.
Divide into 3 portions.
Let all the layers cool.
Spread 1/3 of the butter cream on the nut layer.
Stack a biscuit layer on top.
Sprinkle the biscuit layer with Kirsch then spread on the next 1/3 butter cream .
Lay the second nut layer on top.
Spread the remaining butter cream on top and on sides.
Dust the top with the powdered sugar.
Sprinkle the sides with nuts.
Using a knife mark the top, powdered sugar in diamond.