1/2 cup rice vinegar
1/4 teaspoon salt
2 teaspoons Dijon mustard
1/8 teaspoon freshly ground white pepper
2 teaspoons sugar
1/4 large red onion, thinly sliced into rounds
2 tablespoons finely chopped dill plus more dill sprigs for garnishing
2 hothouse cucumbers
Freshly ground black pepper
In a small bowl, whisk together the vinegar, salt, Dijon mustard, white pepper and sugar. Drop in the onion slices and dill and combine well. Let sit for 20 to 30 minutes.
Meanwhile, wash the cucumbers and use a mandolin or food processor (or a sharp knife and steady hand) to slice them very thin. Place them in a large bowl, toss them well with the onions, their liquid and black pepper to taste, making sure to coat all the cucumbers. Adjust seasoning, place in a serving bowl and garnish with dill sprigs. Serve immediately for a fresher taste, or let sit an hour or two for a more marinated salad.