First mix butter, icing sugar, condensed milk, oil and peppermint oil with the dough hooks of the mixer, then knead briefly with your hands to a smooth mixture. Cover and chill for approx. 30 minutes.
Line two large kitchen shelves or trays with baking paper (they must fit in the refrigerator) Form 55-60 walnut-sized balls from the mixture. Place them on the boards, press them slightly flat (each approx. 4 cm Ø).
Chill for about 2 hours.
Chop the chocolate coating and melt in a hot water bath with coconut oil. Distribute evenly in small bowls and colour each with food colouring red, blue, green and yellow. Use a fork to pull the drops through the chocolate coating and let them drain.
Leave to dry on a cake rack - keep in a cool place for about 1 week.