Soak 10 speculoos in amaretto (for the non-alcoholic version with milk) and mash, then mix with the low-fat quark. Sweeten with sugar as you like (be careful, the speculoos themselves are already sweet). Whip the cream and fold into the cream. Soak the remaining speculoos in the milk (if you want, you can also add some amaretto here) and mash it.
Prepare four large glasses. Alternately fill in a layer of speculoos quark cream and soaked speculoos. Finally sprinkle with some crumbled speculoos and serve chilled.