Preheat the oven to 250 degrees F. Combine the potatoes, garlic, bay leaves and peppercorns in a large pot. Add 2 tablespoons salt and enough water to cover the potatoes by 1 inch. Bring to a boil, then reduce the heat to a simmer and cook until the potatoes are tender, about 15 minutes. Remove the potatoes to a paper towel?lined plate with a slotted spoon; gently blot dry (it?s OK if some of the potatoes crumble). Let cool completely.
Set a wire rack on a rimmed baking sheet. Melt the schmaltz in a large pot or Dutch oven over medium heat (you should have about 2 inches in the pot) and heat until a deep-fry thermometer registers 350 degrees F. Working in batches, fry the potatoes until browned and crisp, 4 to 6 minutes. Remove to the rack with a slotted spoon and immediately sprinkle with salt. Keep warm in the oven between batches.
Add the parsley and sage leaves to the hot schmaltz and fry a few seconds until just crisp. Remove to a paper towel?lined plate with a slotted spoon and sprinkle with salt. Top the potatoes with the fried herbs.