4 pounds potatoes (I like tiny Yukon golds, but you can use whatever boiling potatoes you like for salads)
1 3/4 cups Greek yogurt (I used full-fat but I think other fat levels would work)
1/4 cup sour cream
2 tablespoons freshly squeezed lemon juice (from half a big lemon)
1 tablespoon white wine vinegar
1 tablespoon minced fresh dill
1 medium garlic clove, minced
2 teaspoons kosher salt (I use Diamond brand; use less if you use another, read why here)
Freshly ground black pepper
1 hothouse or English cucumber (1 pound), unpeeled but quartered lengthwise, seeds removed

More ideas for additions: Crumbled feta, chopped green olives, chopped fresh mint leaves or a minced hot chile