Oh.

[ He hears his brother's confusion, offers him a smile. ]

It's just called "hit". You don't actually hit it, you just push the button with your finger.

[ Guess who DID hit it and then had to be hastily corrected so he didn't break the oven by punching it every time. ]

Right. We can have tea while it's cooking and prep some other things.

[ He moves back over to the potato he had been washing, adding another. Then holds out a fork to his brother. ]

Here, stab this into the washed one a few times.