5 large cucumbers, peeled, quartered lengthwise, and seeded
1 bunch scallions
1 bunch dill, ends picked
1 clove garlic, chopped
Juice of 3 large lemons
4 cups buttermilk
1 cup plain yogurt
Freshly ground white pepper
Dash of Tabasco
Thinly slice half of the cucumbers crosswise. Thinly slice half of the scallions crosswise. Set aside.
Coarsely chop the remaining cucumbers and scallions and transfer to a large bowl. Add the dill, garlic, lemon juice, buttermilk, and yogurt, and give a good but gentle stir. Season with salt and pepper and puree in a blender until liquefied. (NOTE: You can use a food processor, but a blender will give a smoother, more pleasing result.)
Transfer the soup to a large bowl and add the reserved sliced cucumbers and scallions. Adjust seasoning with salt, pepper, and Tabasco to taste. Chill for at least 2 hours in the refrigerator.