1. Make the gnocchi: Preheat oven to 375 degrees. Spread 2 cups salt on a rimmed baking sheet. Place potatoes on top of salt, and bake until tender, about 1 hour. Let cool slightly, then peel. Press potatoes through a ricer onto a clean baking sheet, and spread loosely. Let cool.

2. Turn potatoes onto a surface, shape into a mound, and form a well in the center. Pour egg into well, add remaining 2 teaspoons salt, and mix with a fork. Add flour gradually, kneading by hand until just combined.

3. On a lightly floured work surface, divide dough into 10 pieces. Roll each into a 1/2-inch-thick rope. Cut ropes into 1/2-inch pieces. Press each piece to make a depression in the center, or press gently against tines of a fork. Arrange on a lightly floured baking sheet in a single layer. Cover with plastic, and freeze for at least 1 hour (or up to 3 months).

4. Make the ragu: Reduce oven temperature to 300 degrees. Heat oil in a large Dutch oven over medium-high heat. Season veal generously with salt and pepper. Working in batches, cook until golden brown, 4 to 5 minutes per side. Transfer to a plate. Reduce heat to medium. Add onion and garlic, and cook until softened, about 4 minutes. Stir in tomato paste, and cook for 2 minutes. Add carrots and celery, and cook for 4 minutes. Stir in wine, bring to a boil, and cook for 1 minute.

5. Add browned veal, tomatoes, stock, bay leaf, and thyme. Bring to a simmer, cover, and transfer to oven. Cook until veal is very tender, 2 1/2 to 3 hours. Using a slotted spoon, transfer veal to a dish, reserving liquid. Skim fat from liquid. Discard bay leaf and thyme. Remove meat from bones, shredding into bite-size pieces. Return to pot. Season with salt and pepper.

6. Bring a large pot of salted water to a boil. Cook a few gnocchi at a time, stirring gently. Cook just until they float, 3 to 4 minutes. Transfer gnocchi to a colander to drain. Divide gnocchi among bowls, toss with ragu, and sprinkle with Parmesan.