Preheat the oven to 425°F (220°C). Line a baking sheets with parchment paper.

Place the potatoes in a large pot and cover with cold water. Bring to a boil and cook for 12-15 minutes, or until fork tender. Drain well.

Arrange the potatoes on the baking sheets. Using the bottom of a glass or measuring cup, gently smash each potato until about 1/2-inch thick.

Drizzle with olive oil and sprinkle with salt and pepper.

Roast for 35-40 minutes, flipping once halfway through, until the potatoes are deep golden brown and crispy around the edges.

While the potatoes cool slightly, whisk together the mayonnaise, sour cream, Dijon mustard, lemon juice, garlic powder, salt, and pepper in a large bowl.

Add the green onions, dill, and parsley to the dressing and stir to combine.

Once the potatoes are cool, gently fold them into the dressing mixture, leaving some pieces intact and allowing a few crispy bits to remain exposed.

Serve immediately for maximum crispness, or refrigerate for up to 2 hours before serving.