Grind glucose biscuits to a fine powder in a mixer & keep it aside in a bowl.

Grind sugar separately to a fine powder in a mixer & keep it aside in a bowl.

Sieve the above two separately so that the end powder is really fine.

Now, in a mixing bowl, put 1 cup of fine powdered glucose biscuit, 1 cup of fine sugar powder, 4 tbsp of cocoa powder & mix well.

To this fine mixture, add little by little coffee decoction & make it into a dough (like chapathi dough consistency).
NOTE: please don't add water for any reason.

Divide this dough into 2 big ball like portions.

Take each ball & make it flat(by hand) like a small pancake.

Take a chapathi board, put a plastic foil on it, above that, put this pancake, then above that, put another plastic foil and roll the pancake evenly into a big circle(just like you roll chapathi).

In the meanwhile, take another mixing bowl, put together the butter, 10 -12 tbsps of the remaining powder sugar & the vanilla essence. Beat it really well such that it becomes like icing cream.

Now, remove the top plastic foil, & spread this icing butter thick & evenly on the pancake.

Next, hold the bottom plastic foil, & roll the pancake slowly & carefully with the plastic foil.

Repeat the same for the other ball too.

Refrigerate these two rolls in the freezer for about 25-30 mins.

After that, remove the roll from the plastic foil, cut the rolls into small pieces & serve it.

Refrigerate it all the time.