화중지병이 · 화중지병을
pie in the sky, something you can't actually have
Example
돈이 없으면 그 계획은 화중지병일 뿐이에요.
Without money, that plan is just pie in the sky.
Word parts
화 picture+중 inside+지 of+병 rice cake
Literally 'a rice cake in a painting.'
Good to know
Everyday Korean says 그림의 떡 instead.