Makes 1-1/4 cups dressing. Salad serves 4.
For the salad:
1 large seedless (English) cucumber, or several small seedless cucumbers
1 tsp kosher salt
For the buttermilk herb dressing:
2-1/2 Tbsp powdered buttermilk
1/4 cup mayonnaise
2 Tbsp Greek yogurt
1 tsp lemon juice
1/4 tsp Colman's (dry) mustard
2 heaping Tbsp fresh dill
2 heaping Tbsp flat-leaf parsley
1 Tbsp roughly chopped chives
1/4 tsp fresh black pepper
Cut the cucumber into 6-inch pieces, and slice the pieces lengthwise on a mandoline; if you can set the thickness, set it at 1/8-inch to make thin ribbons. Place the cucumber ribbons in a colander, and sprinkle with the kosher salt. Set the colander over a bowl, and let it sit for 20 minutes. Rinse off the excess salt, and dry with a clean dish towel. Place the cucumber in a mixing bowl.
In a blender, combine all of the buttermilk herb dressing ingredients. Add 1/4 to 1/2 cup of water (use less for a thicker dressing). Whiz until the herbs are chopped and the dressing is thoroughly incorporated. Pour as much as needed over the cucumber ribbons, and reserve the rest in the refrigerator for another use.