Preheat the oven to 250°F. line a baking sheet with several layers of paper towels, and set a wire rack inside another. Peel the potatoes. Using the large holes of a box grater or the grater disk on a food processor, grate the potatoes and onion. Transfer to a clean kitchen towel. Gather the ends of the towel and twist to squeeze out as much liquid as possible into a large mixing bowl. Open the towel, toss the potato mixture, then repeat. Wait a few minutes to allow the potato starch to settle, then pour off the liquid in the bowl, reserving the potato starch that sticks to the bottom. Add the potatoes, onions, egg, matzo meal (or breadcrumbs), salt, and pepper to the bowl. Use your hands to blend the latke mixture until all of the ingredients are evenly distributed. Let the mixture rest for 10 to 15 minutes.

In a cast iron skillet, add ¼ inch of shmaltz and/or oil and heat over medium-high heat until a piece of latke mixture sizzles when added to the skillet. Working in batches, scoop about ¼ cup of latke mixture into the skillet and press it with a fork or slotted spatula to flatten slightly. Cook the latkes until deeply golden brown, about 4 to 5 minutes per side. Transfer the latkes to the paper towel–lined to drain, then transfer to the wire rack. Season with salt to taste. Keep warm in the oven until all of the latkes are cooked. (The cooked latkes can also be made a day or two ahead of time; wrap in paper towels, cover and refrigerate. Reheat and re-crisp in a 425°F oven or medium-hot, dry skillet.)

Arrange the latkes on a platter and top each with a dollop of creme fraiche, a spoonful of caviar, and a sprinkle of chives. Serve.