Preheat to 450°, and use the middle rack. Place potatoes in a large pot and cover with water. Add 1 cup of salt and 1 tablespoon of vinegar, and bring it to a boil.
Immediately reduce heat to medium-low, bringing it down to a simmer, and cook until potatoes are just cooked through and pierced easily with a fork, about 15 minutes. Time will vary depending on the size of the potatoes; be careful not to overcook as they’ll fall apart when smashed. Drain and return the potatoes back to the pot to cool and dry out. Dryness will ensure crispy potatoes!
Place another rimmed baking sheet on top, then push down firmly to smash the potatoes (alternately, use the bottom of a mug or measuring cup to smash each one individually).
Drizzle ⅓ cup of extra virgin olive oil over potatoes, then toss to coat; season well with salt and black pepper. Roast potatoes until crispy and golden brown, 35–40 minutes.
Smokey Walnut Sauce
Meanwhile, chop the walnuts and add them along with the smoked paprika, cayenne, and ½ cup olive oil in a small saucepan over medium-low heat, stirring occasionally, until the walnuts turn golden brown, about 6 to 8 minutes.
Remove from heat, and while still hot, grate garlic cloves directly over the hot oil, and toss to combine. Season with salt.
Spread sour cream on a large serving platter. Top with potatoes, and sprinkle some crystal salt and the zest of a lemon, then finish by spooning the walnut sauce over. Scatter herbs all over and serve with lemon wedges alongside.
I use basil and thyme, but I'm sure chives and dill would be fantastic!