Place the dried lobster mushrooms in a bowl and cover with 4 cups of water. Let soak for 20 minutes.

Remove the mushrooms from the water, reserving the soaking liquid. Squeeze out any excess water from the mushrooms and slice them thinly.

In a medium saucepan, combine the mushroom soaking liquid, soy sauce, rice vinegar, and grated ginger. Bring to a boil, then reduce heat and simmer for 10 minutes.

Add the sliced mushrooms and cubed tofu to the saucepan. Simmer for another 5-10 minutes, or until the tofu is heated through and the flavors have melded.

Garnish with sliced scallions and serve hot.