To the flour, add the egg, oil, a pinch of salt and enough lukewarm water to make an elastic dough; rest, then roll out thinly (or use ready-made strudel pastry).
Let the rolled-out dough dry slightly, then cut into equal sheets to fit the baking tray.
Make the ham filling: mix the ground ham with the egg yolks, butter and sour cream, then gently fold in the stiffly whisked egg whites.
Line the bottom of a greased tray with the first sheet of dough.
Spread with a portion of the ham filling, then drizzle with a little sour cream.
Place the next sheet of dough on top, and continue layering in this way until the filling and dough sheets are used up.
Top with a final sheet of dough, and brush generously with melted butter.
Bake in a 180°C preheated oven for 35-40 minutes, until the top is nicely golden-red.
Cut into even squares, and serve warm.
Based on: Malatinszky Fanny szakácskönyve (a classic Hungarian cookbook), modernised. Calories and protein are estimated.