haha wa tsumetai toufu ni shouyu o kakete, watashi ni dashimasu.

My mother pours soy sauce on cold tofu and serves it to me.

Breakdown of haha wa tsumetai toufu ni shouyu o kakete, watashi ni dashimasu.

• は: topic particle
• を: direct object particle
• 母はは: mother
• に: indirect object particle

Questions & Answers about haha wa tsumetai toufu ni shouyu o kakete, watashi ni dashimasu.

Why is it 母は and not 母が?

は marks 母 as the topic: As for my mother, ...

So the sentence is presenting what the mother does. In many beginner sentences, は is used this way to set the scene.

If you used 母が, it would put more focus on mother as the subject, as if answering Who does this?
For example:

• 母は冷たい豆腐にしょうゆをかけて、私に出します。
  As for my mother, she puts soy sauce on cold tofu and serves it to me.
• 母が冷たい豆腐にしょうゆをかけて、私に出します。
  My mother is the one who puts soy sauce on it and serves it to me.

Both can be grammatical, but は is the more neutral choice here.

Does 母 mean my mother? Why not お母さん?

Yes, here 母 normally means my mother.

In Japanese, when talking about your own mother to someone else, you often use:

• 母（はは） = my mother

But when addressing your mother directly, or when referring to someone else’s mother politely, you often use:

• お母さん（おかあさん）

So:

• 母は... = My mother...
• お母さん、これ見て。 = Mom, look at this.

This is a common social nuance in Japanese.