Preheat oven to 425F. Line a large baking sheet with parchment paper.
Boil potatoes in a large pot for 7 minutes, or until fork tender. Drain and allow to cool slightly before transferring them to the being sheet.
Using the bottom of a glass, smash each potato flat. Brush or spray them with olive oil and season with salt and pepper, to taste. Roast for 50 minutes to 1 hour or until golden brown and crispy.
Meanwhile, whisk together the yogurt, mayo, dijon, lemon juice, vinegar, garlic, dill, parsley, salt and pepper to taste.
Mix in the seeded, chopped cucumber and shallots, then cover and refrigerate while the potatoes roast.
Once the potatoes have cooled for 5 minutes, fold them into the dressing so that they are completely coated. Garnish with crispy potato bits, dill and black pepper.