3 large russet potatoes (about 2 pounds)
1 tablespoon kosher salt
1 medium yellow onion, finely grated
1 large egg, lightly beaten
½ cup all-purpose flour
3 cups duck fat (or vegetable oil)
1 pound tart apples (such as Granny Smith or Gravenstein)--peeled, cored and cut into 1-inch cubes
1 pound ripe quince--peeled, cored and cut into 1-inch cubes
2 whole star anise
2 whole cloves
1 cup Vin Santo
4 cups water
¼ cup granulated sugar
1 teaspoon kosher salt
1. Add the potatoes to a large pot; fill the pot with enough cold water to cover the potatoes by a couple of inches. Bring to a boil, then immediately turn off the heat, drain the potatoes through a colander and transfer to a plate. Refrigerate the potatoes overnight.
2. Make the apple-quince conserva: In a large saucepan, add the apples, quince, star anise, cloves, Vin Santo and water. Bring to a boil over high heat. Reduce the heat to low and simmer until the fruit completely breaks down, 20 to 25 minutes. Return the heat to medium and cook, stirring frequently until the fruit thickens and takes on a deep red hue. Add the sugar and season with salt and stir to combine. Return the mixture to a boil and cook until the sugar dissolves and the texture of the conserva is thick. Place a fine-mesh strainer over a medium bowl and use a rubber spatula to press the mixture through the sieve.
3. The next day, peel the potatoes with a paring knife and use the coarse side of a grater to grate the potatoes (or the large shredder attachment on a food processor). Season with salt. Add the grated onion to a fine-mesh sieve and set over a medium bowl. Use a spatula to press the water out of the onions and discard the water. Add the onions and the egg to the potatoes and use a fork to mix. Sprinkle in the flour and mix gently until there are no dry patches of flour remaining.
4. Preheat the oven to 325°. In a large, wide pot, heat the duck fat until it reads between 350° and 370° on an instant-read thermometer.
5. Gently form a good handful of the potato mixture into a latke (about ¼ cup of potatoes per latke), using your hands to compress it into a ¼-inch-thick disc, leaving the edges a bit loose and scraggly.
6. Gently transfer a few latkes to the hot duck fat, leaving plenty of space around each one. Cook until both sides are golden, 3 to 4 minutes per side. Use a frying spider or metal spatula to transfer the latkes to a paper towel-lined baking sheet. Keep warm in the oven while you fry the rest of the latkes. Sprinkle with kosher salt and serve warm with apple-quince conserva.