Transfer the biscuits and melted unsalted butter to a blender. Blend into a fine crumble. Then cover the bottom of a springform tin with baking paper, secure it and spread the buttery cookie crumble on top using the back of a tablespoon. Place it in the fridge to set.

Add the egg yolks and caster sugar to a large mixing bowl.

Whisk well for a minute until the yolk mixture starts to turn pale and the sugar has more or less dissolved. Add the cornstarch, flour, quark cheese and a pinch of salt.

Stir well until you get a creamy batter. Beat the egg whites until stiff and add this to the cheesecake batter.

Gently stir until the egg whites are fully incorporated. Then pour the cheesecake batter on top of the chilled cookie base. Spread the top evenly.

Bake the cheesecake in a preheated oven at 356°F (180°C) for about 45 minutes. Turn off the heat but let the cheesecake in the hot oven for another hour. Place a sheet of tinfoil on top to prevent it from burning. Then remove the cheesecake from the oven, sprinkle with icing sugar and serve.