Let the berries thaw. Mix the quark with the yoghurt, sugar, vanilla sugar and 2 packets of whipped cream to a cream. Whip the cream with the other 2 packets of cream stabilizer, fold in.
Layer in a large bowl: first line the base with speculoos, spread a layer of berries on top, then a layer of curd cream. Continue like this until everything is used up, top off with a layer of cream. Let rest in the refrigerator for about 5 hours.
Sprinkle with crushed speculoos before consumption (optionally with cocoa powder, chocolate shavings, roasted almonds or cinnamon, but I found the crispy crumbs on it very, very good - and was not alone with it).