Heat oven to 450F.
Place the potatoes in a large pot of cold salted water and bring to a boil.
Cook for approximately 8-10 minutes or until just fork tender.
Drain and place the potatoes back in the hot pot.
Add 2 tablespoons of duck fat, and the smashed garlic cloves and combine with the hot potatoes. Allow to cool down, and for fat to infuse, for 15 minutes.
Drizzle baking pan with about 1 tablespoon of duck fat.
Transfer potatoes on baking sheet and with the help of a potato masher,or a fork very gently smash each potato.
Drizzle another tablespoon of duck fat over the smashed potatoes and add freshly ground black pepper, and salt.
Bake 20-25 minutes, turning them over at the half way mark.
Once they are golden brown, and crispy, remove from the oven, toss to coat with lemon juice, fresh parsley, and Parmesan cheese, if desired. Serve immediately.