Learn Hardcore Japanese: asa ha gohan wo taku aida ni, misosiru no zyunbi wo simasu. - In the morning, while the rice is cooking, I prepare the miso soup.

Breakdown of asa wa gohan o taku aida ni, misoshiru no junbi o shimasu.

Why is は used after 朝?

朝は sets morning as the topic: as for the morning or in the morning.

It often has a slight contrastive feel too, as if the speaker is talking about what happens in the morning as opposed to other times of day.

So 朝は is more than just a time expression; it frames the sentence as speaking about mornings.

Why is ご飯を used before 炊く? I thought を marks the object of the main verb.

Here, ご飯を炊く is a smaller clause inside the sentence, meaning to cook rice.

That whole clause modifies あいだに:

ご飯を炊くあいだに = while cooking rice / during the time when rice is being cooked

So を is still marking the object of 炊く, even though 炊く is not the main verb of the whole sentence.

The overall structure is:

What does あいだに mean here, and why isn’t it just あいだ?