4 pounds russet or Yukon Gold potatoes, peeled and cut into quarters, or smaller
5 tablespoons extra-virgin olive oil
Small handful picked rosemary leaves, finely chopped
3 medium cloves garlic, minced
Freshly ground black pepper
Adjust oven rack to center position and preheat oven to 450°. Heat a large pot of water over high heat until boiling. Add 2 tablespoons of kosher salt, 1/2 teaspoon of baking soda, and potatoes and stir. Cook until a knife can easily pierce a potato chunk, about 10 minutes.
Meanwhile, combine olive oil with rosemary, garlic, and a few grinds of black pepper in a small saucepan and heat over medium heat. Cook, stirring constantly, until garlic just begins to turn golden, about 3 minutes. Don't burn it! Immediately strain oil through a fine-mesh strainer set in a large bowl. Save garlic/rosemary mixture for later.
When potatoes are cooked, drain and transfer to bowl with infused oil, plus salt and pepper. Here's where the magic happens: toss potatoes to coat, shaking bowl roughly, until a thick layer of mashed potato–like paste has built up on the outside of the potato chunks. You might think you are over doing it, but you're not. This is how you build up the surface area that will get extra crispy.
Transfer potatoes to a large rimmed baking sheet with parchment paper and spread them out evenly. Transfer to oven and roast, without touching, for 20 minutes. Toss potatoes, flipping them around as you go. Continue roasting until potatoes are deep brown and crisp all over, 20-30 minutes longer.
Transfer potatoes to a large bowl and add garlic/rosemary mixture as a topper. Toss to coat and season with more salt to taste. Serve immediately.