Break up the chocolate into small pieces
Pour chocolate into a pot with the butter and melt on low heat
Cut the seal off of the resealable food bag
Arrange six digestive biscuits flat inside the food bag
Repeat for all biscuits: Crash a rolling pin down on the biscuits several times to break them up, then roll until all biscuits are relatively uniformly crushed into very small pieces, mixing each batch into the pot as you go
Add the raisins and condensed milk to the pot and mix until fully consistent
Cover a baking tray with aluminium foil, then pour the mixture from the pot into the tray
With a silicone spreader, gently spread the mixture until it covers the whole inside of the tray with a roughly even height
Place in fridge for several hours to cool
Once cold, slice into equal-size squares with a knife
Place sheets of kitchen towel inside of a tub and arrange each slice inside the tub