Preheat the oven to 175 ° C top / bottom heat. Grease a springform pan (in a 28 form it becomes a flat fruit base).
Melt the fat. Beat the egg whites until stiff.
In another bowl, stir the egg yolks with 4 tablespoons of cold water until creamy and then slowly pour in the sugar. Let the fat cool down briefly and add to the egg mixture. Add the sifted flour and cornstarch and very carefully fold in together with the egg whites.
Pour the mixture into the springform pan and put it in the oven immediately (otherwise the dough will collapse and the base will not become loose!).
Bake for about 30-40 minutes.
After cooling, top with fruit to taste.
Note: You can also bake the base in a smaller form, then divide it and fill it with cream or cream.