What's the most amount of chocolates you have received on Valentine's Day up to now?
What's the largest amount of chocolates you have ever gotten on Valentine's Day until this year?
この場合、次のような言い方ができますよ。
ーWhat's the most amount of chocolates you have received on Valentine's Day up to now?
「今までバレンタインに最高何個チョコレートをもらいましたか？」
What's the most amount of XX you have received ...? を使った聞き方。
ーWhat's the largest amount of chocolates you have ever gotten on Valentine's Day until this year?
「今までバレンタインに最高何個チョコレートをもらいましたか？」
What's the largest amount of XX you have ever gotten ...? を使った聞き方。
ご参考まで！
カナダ 
