idiom: to find something extremely delicious (literally 'one's cheek would fall off')
このケーキ、ほっぺたが落ちるほど美味しいよ。
This cake is so delicious you'll think your cheeks will fall off.
母の作る料理はいつもほっぺたが落ちる。
My mother's cooking is always delicious.
レストランの評判どおり、ステーキはほっぺたが落ちるほどだった。
As the restaurant's reputation claimed, the steak was incredibly delicious.