Make the short ribs: Season the short ribs with the salt and pepper. Heat the oil in a large heavy-bottomed pot, such as a Dutch oven, over medium-high heat. Once the oil is hot, carefully add the short ribs and cook, turning occasionally, until nicely browned on all sides, about 5 minutes per side. Transfer the meat to a plate and reduce the heat to medium.

Add the onion and garlic to the pot and sauté until soft and light gold but not browned, about 15 minutes.

Return the short ribs to the pot and add the allspice and enough water to come about three-quarters of the way up the sides of the pot. Bring to a boil, cover the pot, and reduce the heat to medium-low, adjusting it if necessary so the liquid simmers gently. Cook the short ribs for about 1 ½ hours and then, using a pair of tongs, carefully turn the short ribs. 

Continue cooking the short ribs, partially covered, for another 1 to 1 ½ hours, until the meat is very tender and the liquid has reduced and thickened slightly. Remove from the heat. 

Let the short ribs partially cool in their liquid and then spoon off the fat that rises to the surface. Once the short ribs are cool enough to handle, take them out, shred the meat, and discard the bones; set aside. If the cooking liquid seems watery, return it to the stove and simmer for a few minutes to thicken and concentrate the flavors. Taste and season with more salt and pepper if needed. (You can cook and shred the short ribs ahead of time, then refrigerate the meat and the cooking liquid separately. Just before serving, remove any remaining fat that's hardened on the cooking liquid, and gently reheat the meat in a bit of the liquid.)

Make the latkes: Grate the onion and then the potatoes on the large holes of a box grater or in a food processor fitted with the shredding blade. Put the grated onion and potatoes in the center of a clean dish towel, wrap them in the towel, and twist it over a large bowl to squeeze out as much liquid as possible, capturing the liquid in the bowl; set the bowl aside. Put the squeezed onion and potatoes into another large bowl.

After about 5 minutes, the potato starch in the liquid will have settled at the bottom of the bowl. Gently drain off the water, leaving the starch behind, then scrape the potato starch into the bowl with the onion and potatoes. Add the flour, whole egg, egg yolk, salt, and pepper and mix until well combined. 

Preheat the oven to 350°F. Line a tray with paper towels.

Place a large skillet over medium-high heat, add about 1 inch of oil, and heat until hot. To check whether the oil is hot enough, drop a few shreds of potato into the oil. If they sizzle briskly, the oil is ready; if not, keep heating it. (If you try to dry the latkes in oil that's not hot enough, they will be heavy and greasy.)

Once the oil is hot enough, scoop out about 1 ½ tablespoons of the latke mix, put it in your palm, and shape it into a flat disk about 3 inches wide. Gently slide the latke into the oil. Repeat the process, adding 4 or 5 more latkes to the pan, taking care not to overcrowd the pan. Fry the latkes, turning once, until golden brown on both sides, about 5 minutes per side. Transfer to the paper towel-lined tray and continue frying the latkes in batches. 

Bake the latkes and short ribs: Arrange the latkes in one layer in a couple of shallow baking dishes, such as 9-by-13-inch Pyrex dishes. Place a small mound of the shredded short ribs on each latke and spoon the short rib cooking liquid over the latkes. 

Bake until the latkes have absorbed some of the cooking liquid and everything is nicely heated through, about 15 minutes.

Garnish the dish with dill sprigs and serve hot.