Preparation

• Adjust oven rack to center position and preheat oven to 450°F (230°C) or 400°F (200°C) if using convection.
• Heat water in a large pot over high heat until boiling.
• Add kosher salt, baking soda, and potatoes; stir and return to a boil.
• Reduce to a simmer and cook until a knife meets little resistance, about 10 minutes after returning to a boil.
• Meanwhile, combine olive oil, duck fat, or beef fat with rosemary, garlic, and black pepper in a small saucepan and heat over medium heat, stirring until garlic is golden, about 3 minutes.
• Strain oil through a fine-mesh strainer into a large bowl and set garlic/rosemary mixture aside.
• Drain potatoes carefully and let them rest in the pot for about 30 seconds.
• Transfer to the bowl with the infused oil, season with additional salt and pepper, and toss to coat.
• Transfer potatoes to a large rimmed baking sheet, spreading them out evenly.
• Roast potatoes without moving them for 20 minutes.
• Shake the pan and turn potatoes using a thin, flexible metal spatula; continue roasting until deep brown and crisp, about 30 to 40 minutes longer.
• Transfer potatoes to a large bowl and add garlic/rosemary mixture and minced parsley; toss to coat and season with more salt and pepper.
• Serve immediately.