Adjust the oven rack to the center position and preheat your oven to 450°F (230°C) or 400°F (200°C) if using convection. Bring 2 quarts of water to a boil in a large pot over high heat. Add 2 tablespoons kosher salt, 1/2 teaspoon baking soda, and the peeled and chunked potatoes. Stir well, then return the mixture to a boil. Lower the heat to a simmer and cook until a knife meets little resistance when inserted into a potato chunk, about 10 minutes after the water returns to a boil.

While the potatoes cook, combine the olive oil (or duck fat, goose fat, or beef fat), finely chopped rosemary, minced garlic, and a few grinds of black pepper in a small saucepan. Warm over medium heat, stirring and swirling the pan, until the garlic just begins to turn golden, about 3 minutes. Immediately strain this oil through a fine-mesh strainer into a large bowl, reserving the strained garlic and rosemary mixture separately. I like to strain right away to prevent the garlic from turning bitter.

Once the potatoes are tender, drain them carefully and let them rest uncovered in the dry pot for 30 seconds to allow excess moisture to evaporate. Transfer the potatoes to the bowl with the infused oil. Season with additional salt and pepper as needed, then toss and shake the bowl vigorously until a thick layer of mashed potato–like paste coats the chunks. This roughing-up step helps to create that wonderfully crispy crust during roasting.

Spread the oil-coated potatoes onto a large rimmed baking sheet in a single layer, making sure they are not crowded. Roast in the preheated oven for 20 minutes without moving them. Then, use a thin spatula to carefully lift any stuck potatoes, and shake the pan to turn the pieces. Continue roasting, turning and shaking the potatoes a few times, until they are deep brown and crisp all over—this usually takes another 30 to 40 minutes. For extra crispiness, I like to roast them on convection if your oven allows.

Transfer the roasted potatoes to a large bowl. Add the reserved garlic and rosemary mixture from Step 2 and sprinkle with the chopped parsley. Toss well to coat, then season with additional salt and pepper to taste. Serve immediately for best results—I find these are best enjoyed hot and crisp right from the oven!