Preheat the oven to 450°F (230°C) or 400°F (200°C) for convection ovens.
Bring 2 quarts (2 liters) of water to a boil in a large pot. Add kosher salt, baking soda, and potatoes.
Return to a boil, reduce heat, and simmer for about 10 minutes until potatoes are tender when pierced with a knife.
While the potatoes cook, combine olive oil (or chosen fat), rosemary, garlic, and black pepper in a small saucepan.
Heat over medium heat for about 3 minutes, stirring constantly until the garlic starts to turn golden.
Strain the oil into a large mixing bowl and reserve the garlic-rosemary mixture separately.
Drain the potatoes and let them sit for 30 seconds to release excess moisture.
Transfer potatoes to the bowl with the infused oil. Season lightly with extra salt and pepper if desired.
Toss vigorously until the potato surfaces become rough and coated with a mashed potato-like layer.
Spread the potatoes evenly on a large baking sheet.
Roast for 20 minutes without moving them.
Turn the potatoes using a spatula and continue roasting for 30–40 minutes, turning occasionally, until deeply golden and crispy.
Transfer to a serving bowl and toss with the reserved garlic-rosemary mixture and fresh parsley.
Serve immediately.