Dictionary / Vocabulary / 絵に描いた餅
えにかいたもち
pie in the sky; castles in the air; drawing of a rice cake
Also written 絵に描いた餠、絵にかいた餅
君の夢一杯のビジネスプラン、絵に描いた餅にならんことを切に望むよ。
This business plan of yours seems almost too optimistic. All I can say is I hope it's more than just wishful thinking.