Finely grind the cookies and half of the chocolate with a food processor and place in a bowl.
Melt the remaining chocolate with the butter over a hot water bath and add to the bowl with the crumbs.
Put the Baileys and rum in the bowl and mix well to a smooth mass.
Leave the mass to cool for approx. 2 hours in a refrigerator.
Portion with a spoon about 35-40 pieces from the mass, and form them into balls between your hands.
Roll the balls briefly in the cocoa powder until they are evenly covered. Then place on a plate and let it cool again for about 30 minutes so that they become firm.
Place the finished Baileys balls in a closable container and store in a cool place.