Grind the biscuits until they are super fine. In a big bowl, add all your dry ingredients for the base – the biscuits, the powdered sugar, the coconut flakes, and the cocoa powder – and mix them well. It helps later if you put it in the fridge for a while.

Measure the wet ingredients in a different bowl. Add them to the dry ingredients and mix well.

In another bowl, mix the soft butter and the sugar. Fold the coconut flakes in the butter mixture.

Cover a pastry board with cling wrap. Sprinkle it with coconut flakes so that the base is less sticky. Remove the biscuit base from the fridge and cut it in half. Roll the biscuit base out so that it is roughly square-shaped – you can use a knife to help with the edges. Ideally, it must be 4-5 mm thick. However, you can adjust the thickness to suit your taste.

If it sticks to the rolling pin too much, sprinkle it with coconut flakes or ground biscuits.

Spread half the buttercream evenly on top, then start to roll it with the help of the cling wrap.

Do the same with the other half of the biscuit base and the buttercream. Overnight the rolls in the fridge, wrapped in aluminum foil, so they can be properly set.