Trim the stems of the shiitake mushrooms and slice them thinly. Slice the cucumber thinly as well.

In a bowl, mix the cucumber with salt and massage it gently. Let it sit for 5 minutes, then squeeze out the excess water.

In a separate bowl, mix the sugar, soy sauce, ground white sesame, and dashi stock to prepare the dressing.

Heat salad oil in a frying pan over medium heat. Add the shiitake mushrooms and sauté until tender. Let them cool slightly.