Thinly slice the shallots and place them in Ice water (at least 15 minutes).
Peel and slice the cucumbers to your desired size. the thinner the slice the stronger the flavor will be with the salad dressing.
Mix the rice vinegar, sugar, fish sauce, salt, until everything has dissolved. Then mix in the cucumbers, shallots and cilantro. Top with roasted peanuts if you wish.