日本の食材を使い始めたきっかけは何ですか？って英語でなんて言うの？

1. This is the basic question
2. This is a similar basic question form.
3. This is a little more antagonistic. It assumes the chef thinks Japanese ingredients are good. Maybe the speaker does not share that opinion.

This is simple question to ask for the reason why the restaurant decided to use Japanese ingredients.

I hope this helps :)

You can ask politely why they are using Japanese ingredients.

These are all questions.
Some restaurants might use ingredients and all the above questions relate to ingredients.

Some restaurants might actually be making Japanese meals or dishes. Just change the word ingredients for dishes.

What prompted you to use Japanese dishes? etc

Hope this helps
Jane :)

"what made you" is probably a more polite way to ask this question. Using why might sound too direct.

You can ask the chef any of these questions to get an answer as to why he is using Japanese ingredients:-

1. Is there any special reason why you are using Japanese ingredients?
   日本の食材を使用する特別な理由はありますか？

2. Why did you choose to use Japanese ingredients?
   なぜ日本の食材を使用するのですか？