"Last year, I made so many lasagnas that I thought I might be done with them for life. But here's the thing: lasagna is layers and layers of love, which makes the time you put into it worthwhile." -Rach
For the meat sauce, heat a Dutch oven or other sturdy saucepot over medium to medium-high. Add the EVOO, three turns of the pan. Add the onion, celery, carrot, and garlic; season with salt. Cook, stirring often, until the vegetables soften, 4 to 5 minutes. Add the meat and chicken livers, if using. Cook until the meat is no longer pink, about 6 minutes; season with salt and pepper. Stir in the herbs, then the wine. Cook, stirring occasionally, until the wine is absorbed, 8 to 10 minutes. Add the tomato paste; stir for 1 minute. Add the stock and milk and bring to a bubble. Reduce the heat to low and simmer, stirring occasionally, until the sauce thickens and the vegetables and meat are well combined, 60 to 90 minutes. Remove the sauce from the heat and discard the bay leaf.
For the besciamella, in a large skillet or saucepan, melt the butter over medium to medium-high heat. When the butter foams, whisk in the flour, then whisk in the milk. Season the sauce with salt, white pepper, and the nutmeg. Cook the sauce, stirring often, until it thickens enough to coat the back of a spoon, about 10 minutes. Remove the sauce from the heat.
Bring a large pot of water to a boil for the pasta. Salt the water, add the pasta, and cook for 5 minutes. Drain the pasta and arrange the noodles in a single layer on a kitchen towel. Top with another kitchen towel.
Arrange the oven rack in the center of the oven; preheat to 375°.
Pour half of the passata into a 9-by-13-inch baking dish; spread evenly in the bottom of the dish. Add a layer of noodles (3 noodles per layer) and one third of the meat sauce. Add another layer of noodles, one third of the white sauce, and a handful of Parmesan. Repeat the process two more times. Top with a final layer of noodles and the remaining passata, then top with the mozzarella and the remaining Parm. Cover with foil and bake for 40 minutes. Uncover and bake until brown and bubbly, 20 to 30 minutes more. Let stand until set, 20 to 30 minutes. Slice and serve in shallow bowls. Garnish with the parsley.
Give It a Rest: Unless you want lasagna soup, you need to let your lasagna rest for 20 to 30 minutes before slicing into it. While you wait, have some crostini and a glass of wine.