Preheat & Parboil Potatoes

Adjust oven rack to center position and preheat oven to 450°F (230°C) or 400°F (200°C) if using convection.

Bring 2 quarts (2 L) water to a boil in a large pot over high heat.

Add 2 tablespoons kosher salt (about 25 g), baking soda, and the potatoes; stir and return to a boil.

Reduce heat to a simmer and cook until a knife meets little resistance in a potato chunk, about 10 minutes after boiling returns.

Infuse Fat & Aromatics

In a small saucepan, combine 2 tablespoons olive oil (or duck/beef fat), the rosemary, garlic, and a few grinds of black pepper.

Heat over medium, stirring and shaking constantly, until the garlic just turns golden, about 3 minutes.

Immediately strain the oil through a fine-mesh strainer into a bowl, reserving the garlic/rosemary solids separately.

Toss Potatoes in Infused Oil

Drain the potatoes and let rest in the pot for 30 seconds to evaporate excess moisture.

Transfer potatoes to the bowl with infused oil. Season with salt and pepper, then toss vigorously until a mashed‐potato‐like paste forms on the surface of each chunk.

Roast Potatoes

Spread the potatoes in a single layer on a large, rimmed baking sheet.

Roast without moving for 20 minutes.

Use a thin metal spatula to loosen any stuck pieces, shake the pan, and turn the potatoes.

Continue roasting, turning and shaking every 10–15 minutes, until deep brown and crisp all over, 30–40 minutes more.

Finish & Serve

Transfer potatoes to a large bowl and add the reserved garlic/rosemary mixture and minced parsley.

Toss to coat, taste for salt and pepper adjustments, and serve immediately.