An earthware pot

Do you know for what this pot is?

The other day, my husband bought this pot as Shizusan had asked him to buy.
I had never seen a pot like this till then.
In the middle and lid of the pot, there are some holes for vapor.

I found it was a pot for baking potatoes.

As Shizusan grew lot's of sweet potatoes this year too, I baked some.
They smelled nice and were delicious.