Soak the dried wood ear mushrooms in hot water for 30 minutes to an hour until softened and doubled in volume. Drain. Cut off the tough portions (see full illustration). Tear into bite-size pieces.
While the wood ears bathe in hot water, peel and scoop out the seeds of the cucumber. Cut into slices (what shape or size is up to you).
In an oil-free pan, toast the sesame seeds over medium heat until golden brown and glossy with its own rendered oil.
Make the dressing by stirring together the soy sauce, black vinegar, sesame seed oil and half of the toasted sesame seeds.
Bring a pot of water to the boil. Drop in the rehydrated and trimmed wood ears. Leave for five minutes.
Drain the wood ears, dump into a bowl of iced water then drain again.
Place the wood ears in a bowl. Add the dressing and toss. The wood ears will soak up half of the dressing.
Add the cucumber slices to the wood ears. Toss to blend.
Sprinkle the remaining toasted sesame seeds over the wood ear mushrooms and cucumber salad before serving.