Over medium heat, heat the olive oil in an oven-proof pan until hot but not smoking. Once the pan is ready, add the hare legs and sear until lightly browned on the outside, but not cooked through, about 6-8 minutes each side. Remove the browned meat from the pan. Add the onion, carrots and celery and sauté until the vegetables begin to soften and turn light golden brown, about 5 to 10 minutes. Add the tomato paste and cook for another 10 minutes. Then add red wine, stock, herbs, and season to taste with salt and pepper and bring to a boil. Cook for 10 minutes and then return the rabbit legs to the pan, bring to a boil, lower heat to a simmer, cover and braise in the oven for 1 ½ hours or until the meat comes off easily from the bone. Let cool and remove the meat from the bones and pull into ½ inch pieces. Place meat back into juices and simmer for 20 minutes.
Spread the chestnuts on a baking sheet. (To make peeling them easier, you can cut an X in the flat side of each chestnut with a sharp paring knife.) Roast in a 450ºF oven, turning every 5 minutes or so, for 15 minutes, or until the shells can be easily removed. Place in a food processor and process to a fine crumb consistency and set aside.
Bring 6 quarts of water to a boil in a large pot, and add 2 tablespoons salt. Add the potatoes and cook until tender but not falling apart. Drain and allow to cool for 10 minutes, then peel the potatoes and cut into smaller pieces and pass through a ricer.
In the large bowl, combine the roasted chestnuts, riced potatoes, ricotta, Parmigiano and nutmeg and stir until just homogenous.
Using a pasta machine, roll out the pasta to the thinnest setting and then cut the sheets into 3 inch squares. Place 1 tablespoon of the filling on each square and fold over to form rectangles. Continue filling and shaping until all the pasta and filing are used. Cover and refrigerate until needed or place on baking sheets between layers of dish towels and freeze overnight. The next day, place in freezer bags and store up to 1 week. For a primo course I recommend 7 ravioli per person and a scant ½ cup of ragu per person.
Bring 8 quarts of water to a boil and add 2 tablespoons of salt.
Meanwhile, in a 10-to 12-inch sauté pan, add ragu and heat through thoroughly. Cook the pasta in the boiling water until tender and cooked through, 2 to 3 minutes. Drain the pasta and add to the pan with the sauce. Toss to coat for about 30 seconds and serve immediately with a fresh grating of aged Pecorino.
Pasta Dough Instructions:
Sift flour and cocoa together in a bowl. Mound 3 ½ cups of the flour and cocoa mix in the center of a large wooden cutting board. Make a well in the middle of the flour and add the eggs and the olive oil. Using a fork, beat together the eggs and oil and begin to incorporate the flour, starting with the inner rim of the well.
As you expand the well, keep pushing the flour up from the base of the mound to retain the well shape. The dough will come together when half of the flour is incorporated.
Start kneading the dough with both hands, using the palms of your hands. Once you have a cohesive mass, remove the dough from the board and scrape up and discard any leftover bits. Lightly re-flour the board and continue kneading for 6 more minutes. The dough should be elastic and a little sticky. Wrap the dough in plastic and allow to rest for 30 minutes at room temperature. Roll or shape as desired.