Instructions

1. Heat a medium Dutch oven over medium heat. Add the butter and 2 tablespoons of olive oil and warm until the butter is melted. Add the onions, carrots, celery and ½ teaspoon salt. Cook, stirring often, for 6 minutes or until the vegetables are soft, but have no color. Add the beef and cook, breaking apart the meat with a wooden spoon, for 5 minutes or until the meat is cooked through and no longer pink. Stir the garlic, chili paste and tomato paste into the meat mixture. Cook the tomato paste for 2 minutes, stirring often, to caramelize the tomato paste and gently cook the garlic. Stir in 1/2 teaspoon salt and add the milk. Bring to a simmer and cook for 20 minutes, stirring occasionally until the milk has almost entirely evaporated. Add the wine, tomatoes, bay leaf, and Parmesan rind. Bring to a simmer and reduce the heat to low to  maintain a gentle simmer. Simmer the sauce for 1 1/2 hours, stirring occasionally to prevent sticking. Skim the oil from the surface and season with the remaining 1/4 teaspoon salt. Cool the sauce to room temperature, stirring often, for at least 1 hour. Remove and discard the parmesan rind and bay leaf. The sauce should be cool or just warm to the touch.
2. Bring a large pot of water to a boil and season generously with salt. Cook the pasta until quite al dente, 3 to 4 minutes less than the package directions. Using a spider, remove the pasta to a rimmed baking sheet and cool to room temperature. Reserve and cool 1/4 cup of the pasta water.
3. Ladle 1/2 cup of the sauce on the bottom of a 9x13 inch baking dish and spread evenly. Add the cooled pasta to the cooled sauce along with 1 cup grated parmesan cheese. Toss well to coat. Spoon the mixture into the prepared pan. Sprinkle the top with the remaining 1/2 cup parmesan cheese and the mozzarella. Cover with plastic wrap and place in the refrigerator until ready to serve. Refrigerate the reserved pasta water as well.
4. When ready to bake the pasta, preheat the oven to 375 degrees F. Remove the pan from the refrigerator 30 minutes before baking.
5. Pour 3 tablespoons of the reserved pasta water over the top of the pasta and cover tightly with foil. Bake until the pasta is almost heated through and the cheese is almost entirely melted, about 30 minutes. Increase the temperature to 425 degrees, remove the foil and bake until golden brown and bubbly, another 25 minutes. Allow to rest for 5 minutes before serving.