Heat the oven to 450 degrees.
In a large bowl combine the duck fat, salt, rosemary and thyme. Stir well. Add the potatoes and toss to combine. With a slotted spoon add the potatoes to a rimmed foil lined sheet pan. Place into the oven and roast for 15 minutes. Set the bowl aside to use for later.
Reduce the heat to 425 degrees. Stir the potatoes and continue to cook until crispy, about 25 to 30 minutes. Stirring occasionally.
Meanwhile, add the tarragon and parsley to the mixing bowl with the remaining duck fat and herbs.
Remove the potatoes and place into the mixing bowl. Toss to combine, salt to taste and serve immediately.
