Melt butter in a pot. Grind 300 g biscuits in the universal chopper. Mix butter and biscuits. Spread the bottom of a square springform pan (24 x 24 cm) with oil. Press the crumb mixture in it to a smooth base and refrigerate for about 15 minutes
In the meantime, chop the chocolate coarsely and melt it over a warm water bath. Set aside and let it cool down a little, stirring several times
Separate eggs. Place the egg yolks, low-fat curd, cocoa and 75 g sugar in a mixing bowl and mix well with the whisks of the hand mixer. Carefully allow the melted chocolate to shrink and stir in briefly. Whisk the egg whites and 1 pinch of salt with the whisk of the hand mixer until stiff and quickly fold into the quark and chocolate mixture
Let the mixture run into the springform pan on the crumb base, smooth it down if necessary and bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for approx. 45 minutes on the bottom shelf. Take the cake out of the oven and let it cool down on a cake rack for approx. 1 hour
Soak gelatine in cold water. Put condensed milk and 25 g sugar in a pot. Bring to the boil, simmer for 3-5 minutes, remove from heat and allow to cool slightly. Squeeze the gelatine well and dissolve in the warm condensed milk. Spread the condensed milk over the cake. Chill the cake for about 1 hour. Coarsely crumble 25 g biscuits and roast in a pan without fat for 1-2 minutes, remove. Spread crumbs on the cake, cut into pieces and arrange on a plate
waiting time approx. 1 3/4 hours