Napoleon Cake with Cherry, Nuts, and Poppy-Seed Meringue

Napoleon (a layered pastry dessert)

Ingredients:

Dough: 200g margarine
600g flour
4 egg yolks
4 tbsp sour cream (smetana — a thicker Eastern European-style sour cream)
1 tbsp vinegar
0.5 liters of cherries
200g nuts
100g poppy seeds

Meringue: 2 egg whites
3 tbsp sugar.

Cream: 3 egg yolks
1 cup sugar
3 tbsp flour
0.5 liters milk
300g butter
1 tsp vanilla extract
1/4 tsp citric acid

Dough:
Chop the margarine and flour together.
Add the remaining ingredients.
Knead everything together, divide the dough into 6 portions, and refrigerate the portions.
Roll out 1 portion of dough, place it in a baking dish, and top it with cherries and nuts.
Spread the meringue on top and sprinkle with poppy seeds (not ground).
Roll out another portion to cover the layer.
Prick the top thoroughly with a fork.
Bake the layer.
Repeat with the remaining dough portions.

Meringue:
Whip the egg whites with sugar until stiff peaks form.

Cream:
Add the flour to the whipped egg yolks with sugar, then pour in a little milk to reach a consistency similar to sour cream.
Bring the remaining milk to a boil, pour the boiling milk into the mixture, bring the combined mixture to a boil again, cook it for 5 minutes, then cool the custard.
Add the butter, vanilla extract, and citric acid, and whip the cream until smooth.
Spread the cream between the layers.