Cut the tofu into 1/4-inch thick slices and place them between two pieces of kitchen paper, then place something heavy on top. This will get rid of some of the water in the tofu. Leave like this for 30 minutes.
In a wok, or frying pan large enough to hold the tofu in a single layer, mix the garlic, ginger, sake, tamari, sesame oil, and water. Add the tofu, in a single layer, and bring to a simmer. Cover the wok and leave it to simmer for about 20 minutes or until all the liquid has been absorbed. Turn the slices over once or twice while simmering.
Spread the sesame seeds on a plate. Dip the tofu into the seeds, pressing down firmly, to coat both sides.
Heat the oil in a frying pan and cook the tofu until golden on both sides, a few minutes per side. Serve with noodles or rice and some stir-fried vegetables.