Preheat the oven to 425°F.
Line a large baking sheet with parchment paper. Use two baking sheets if needed to prevent overcrowding.
Place the baby potatoes in a large pot of well-salted cold water.
Bring the water to a boil over medium heat.
Cook the potatoes for 7 to 8 minutes, or until they are just fork tender.
Drain the potatoes thoroughly.
Allow the potatoes to cool slightly.
Pat the potatoes dry with paper towels to remove excess moisture.
Transfer the potatoes to the prepared baking sheet.
Gently smash each potato to approximately 1/4 inch thick using a potato masher or the bottom of a sturdy glass.
Brush the smashed potatoes with 2 tbsp olive oil.
Season the potatoes with 1/2 tsp salt and 1/4 tsp ground black pepper, or adjust to taste.
Roast the potatoes for 45 to 60 minutes, flipping halfway through, until golden brown and crisp.
While the potatoes roast, prepare the dressing.
In a medium mixing bowl, whisk together the remaining 1 tbsp olive oil, Greek yogurt, mayonnaise, Dijon mustard, lemon juice, minced garlic, and chopped parsley until smooth.
Stir in the finely chopped dill pickle and finely chopped shallot.
Taste the dressing and season with additional salt and ground black pepper as needed.
Cover the dressing and refrigerate until the potatoes are fully roasted.
Remove the roasted potatoes from the oven.
Allow the potatoes to cool for approximately 10 minutes.
Reserve a small amount of the crispy browned potato pieces for garnish.
Transfer the remaining roasted smashed potatoes to a large mixing bowl.
Add the prepared herbed yogurt dressing to the potatoes.
Gently toss until the potatoes are evenly coated, taking care not to break them down too much.
Transfer the salad to a serving dish.
Garnish with sliced scallions and the reserved crispy potato pieces.
Serve warm.