Combine the Braised Short Ribs and spinach in a bowl and season with salt and pepper. Set aside.
Bring a large pot of water to a boil and season with salt.
Using a rolling pin and pasta machine, roll out the Fresh Pasta Dough into a long sheet about 1/16 inch thick. Use flour as necessary to keep the surfaces from sticking. With a knife, cut the long sheet into 2 equal sheets. Cut each sheet into 4 equal squares, about 4 inches per side (don't worry if they're slightly rectangular).
Divide the meat mixture among 4 of the pasta squares; the filling should come 1/2 inch from the edges. On each raviolo, press a small hole into the center of the filling and top with an egg yolk. Brush the edges of the pasta with a small amount of water, and top each with another square of pasta. Carefully seal the edges, making sure no air pockets are present.
Blanch the raviolo in the boiling water for 2 minutes, just to cook the pasta and warm the filling through. Transfer to a large saute pan and add the butter, a small amount of the pasta water, the Parmigiano-Reggiano and lemon zest and juice. Reduce the liquid until the pasta is glazed. Serve hot.
Fresh Pasta Dough:
In a mixer with a paddle attachment, combine the flour, egg yolks, milk, olive oil and salt and mix until the dough begins to clump.
Empty the contents of the bowl onto a clean surface and knead until the pasta dough is a smooth yellow and has become elastic, about 2 minutes. If the dough is under-kneaded it will crack when you are rolling it out. Wrap in plastic wrap and let rest 10 minutes before rolling out.
Braised Short Ribs:
One day before cooking, season the short ribs liberally with salt. Allow the meat to marinate in the refrigerator, uncovered, overnight.
The next day, preheat the oven to 250 degrees F. Pat the short ribs dry with a paper towel.
Heat a cast-iron Dutch oven over medium-high to high heat. Add enough canola oil to coat the bottom of the pot and sear the short ribs until they are brown and crusty. Remove the short ribs from the pot and let them rest.
Drain the scorched oil from the pot and add a thin film of fresh canola oil. Add the carrots, celery, garlic, ginger and onions. Reduce the heat to medium and sweat the vegetables until they're translucent. Scrape the bottom of the pot with a wooden spoon to loosen the brown bits. Add the tomatoes and continue to saute until the tomatoes begin to soften and break down. Add the star anise and cinnamon. Add the red wine and let it reduce by half.
Add the short ribs back to the pot and add enough cold water to just cover the ribs. Bring the liquid to a simmer; skim off the scum and then cover the pot. Transfer to the oven and let the short ribs braise until they're nearly falling apart, perhaps 3 hours.
Remove the short ribs from the liquid and let them rest. Strain the braising liquid and then return it to the pot. Discard the solids, except the garlic. Reduce the braising liquid over medium-high heat until it starts to thicken.
Remove the bones and excess fat from the ribs and pull the meat. Add enough of the liquid to the shredded meat to moisten the mixture. Add the braised garlic cloves, mashing them with a fork. Season with salt and pepper as needed. Yield: 6 to 8 servings