For the Stew:
3 tablespoons canola oil, plus up to 3 tablespoons more as needed
3 pounds bone-in beef short ribs, cut into 3-inch pieces
1½ teaspoons kosher salt, plus more to taste
1 medium yellow onion, halved and sliced
2 large red beets, scrubbed well
2 quarts low-sodium beef stock
2 large russet potatoes, peeled and diced into ½-inch cubes and covered in cold water (to prevent oxidation)
1 carrot, peeled and coarsely grated
Freshly ground black pepper, to taste
½ cup chopped scallion
½ cup chopped dill
½ cup crème fraîche or sour cream
Spicy mustard (such as Russian or Chinese)
1 loaf very dark, dense Russian- or German-style bread
1. In a large heavy-bottomed pot or Dutch oven, heat the canola oil over medium-high heat. Season the short ribs with salt and add to the oil, cooking until browned on all sides, 12 to 14 minutes. Remove from the heat and transfer the short ribs to a large plate; set aside. Discard all but ¼ cup of the rendered fat from the pot. If the fat doesn't yield ¼ cup, supplement with canola oil.
2. Return the pot to medium-high heat and add the onions. Cook, stirring often, until golden and tender, 10 to 12 minutes. Remove from the heat, transfer the onions to a medium bowl and set aside.
3. Place the beets in the pot and add the beef stock. Bring to a boil over medium-high heat, reduce the heat to medium, then cook at a simmer, partially covered, for 45 minutes, until the beets are halfway cooked. With tongs, carefully remove the beets and place in a separate medium bowl; set aside.
4. Add the browned short ribs to the broth, along with the reserved onions and diced potatoes, partially cover and cook at a high simmer until the short ribs are very tender, about 3 hours.
5. While the short ribs are cooking, use a paring knife to peel the beets, discarding the skin, and coarsely grate with a box grater.
6. When the short ribs are ready, remove them from the pot, along with any loose bones, and return to the large plate. Add the grated beets and carrots to the pot and simmer until soft, 30 minutes.
7. While the beets and carrots are cooking, pick the meat from the bones and dice, discarding the bones and connective tissue. Add to the pot and adjust the seasoning to taste with salt and freshly ground black pepper.
8. To serve: Ladle the soup into bowls and garnish with the scallions, dill and a dollop of crème fraîche. Serve with spicy mustard and slices of dark bread.