How to make Biscuit Roll

500 g biscuit powder
200 g frosting sugar or powdered sugar
a hint of vanilla sugar or vanilla extract
30 g cocoa powder
6-8 tblspoons milk or coffee

Mix these in a bowl to make a dough - it should be like the one you make for chapati, not too soft. Add more milk or coffee if needed. Divide it into 2 or 3 smaller doughs.
Biscuit powder is not something you get in every store, but you can make it yourself from biscuits like Rich Tea, using a nut grinder.

Now make the filling:
100 soft butter
100 frosting sugar
a hint of vanilla sugar (optional)

Mix them and divide into 2 or 3 parts just like you did with the dough.

Put a dough on a plastic sheet or on a very clean, soft plastic bag and roll it out. Spread the filling all over, then slowly roll it up with the help of the plastic sheet ( leaving the plastic sheet outside the roll). Repeat this with the other dough(s), place them on a plate and put them in the fridge.
After 2-3 hours slice the rolls into pieces with a knife and serve.