一磚豆腐想升仙 [－砖－－－－－]

Jyutping jat1 zyun1 dau6 2 fu6 soeng2 sing1 sin1
Pinyin yī zhuān dòu fu xiǎng shēng xiān

Definitions (CC-CANTO)

(Sarcasm) When someone thinks he/she knows everything by knowing just a part of it