Freeze the tofu.
Let it thaw naturally, lightly drain, and then cut.
Simmer the tofu in your choice of mentsuyu. It's also delicious if you add shiitake mushrooms, leek, eggplant, konnyaku, or your choice of vegetables.
If you buy tofu when it's cheap and freeze it, it really comes in handy when you're in a pinch. It's also money-saving.