Iemand een koekje van eigen deeg geven — “To give someone a cookie of their own dough.” This Dutch idiom means: to give someone a taste of their own medicine; to treat someone the way they have been treating others. The imagery is vivid — you bake someone’s own dough into a cookie and serve it back to them. The English equivalent is exactly “a taste of their own medicine.”
Usage: Hij was altijd onaardig voor anderen, maar nu geven zijn collega’s hem een koekje van eigen deeg. (He was always unkind to others, but now his colleagues are giving him a taste of his own medicine.) The idiom carries a sense of poetic justice — the punishment fits the crime because it literally uses the same material. It is used with a mix of satisfaction and mild reproach.
Idioms involving food in Dutch: Dat is gesneden koek (That is sliced cake = that is easy / a piece of cake), In zijn eigen sop gaarkoken (to cook in your own juices = to let someone deal with their own mess), Iets door de vingers zien (to see something through the fingers = to turn a blind eye — not food, but a hand gesture), De pap wordt te heet gegeten (the porridge is eaten too hot = people are too impatient). Dutch has a rich tradition of practical, domestic idioms.