Make the Bolognese Sauce

1. Cook the soffritto. In a large Dutch oven set over medium-low heat, add the butter, olive oil, and onions, season with salt, and sauté until translucent but not browned and most of the moisture has evaporated (about 10 minutes). Turn up the heat to medium, add the carrots, and cook for 5 minutes. Next, add the celery and cook for 5 minutes more.
2. Cook the pancetta. Add the ground (or finely diced) pancetta to the pot and sauté until cooked through and most of the fat has been rendered (about 10 minutes).
3. Cook the beef. Add 1/2 of the beef to the pot breaking it up into small pieces with the back of a spoon, season with salt and black pepper, and cook until no longer pink and some of the moisture has evaporated, about 5 minutes. Add the rest of the beef, season with salt, and cook until the moisture has evaporated (about 10 minutes).
4. Deglaze the pot with wine. Add the wine while scraping the browned bits (the fond) from the bottom of the pot. Let the mixture cook for at least 20 minutes and up to 25 minutes to allow the alcohol to evaporate.
5. Add the milk, tomato, and broth, and finish the ragù. Add the tomato passata to the pot. Stir the tomato paste into the chicken stock and milk, and add it to the pot. Season with a little salt and black pepper, reduce heat to low, and gently simmer covered, stirring occasionally for approximately 2 1/2 hours. You may add chicken stock  1/4 cup at a time to thin it out only as needed. Turn off the heat, adjust the seasonings, and set aside until ready to assemble lasagna.

*You will need approximately 1 liter (or 4 cups) of this bolognese sauce for the lasagna recipe. Refrigerate or freeze the remaining Bolognese sauce to serve over gnocchi or with tagliatelle pasta. 

Make the Spinach Lasagna Noodles (or skip this step and use ready-to-bake store-bought egg lasagna noodles)

1. Blanch the spinach. Add the frozen spinach to a pot of boiling water and blanch it for about 3 minutes (blanch fresh spinach for 1 minute only). Strain it reserving the liquid being sure to squeeze out all of the excess liquid. Use a blender, immersion blender, or food processor to purée the spinach to a fine paste and set aside. *Alternatively, finely mince the spinach. 
2. Make the dough. Add the flour to a countertop or large bread bowl and make a "well" in the middle. Add the eggs, and spinach to the center and begin agitating the mixture to combine it with the flour being sure to keep everything in the center of the "well". Work in a circular motion incorporating more flour into the center until the mixture is combined and forms a shaggy dough. 
3. Knead the dough.  Remove the dough to a work surface and knead it by turning it clockwise a quarter turn and repeating until the dough becomes softer and more pliable, or about 10 to 12 minutes. It should be much smoother and more elastic at this point.  *Alternatively, you may knead the dough using a stand mixer fitted with the dough hook attachment on medium-low speed (speed #2 on a KitchenAid). 
4. Rest the dough. Cover and rest the dough for 30 minutes. 
5. Roll out the dough. Cut dough into 4 equal pieces. Working with one piece at a time (keep the others covered), flatten into a disc thin enough to feed through the pasta machine's widest setting (0 or 1). Pass the dough through rollers dusting lightly with flour as needed and letter-fold the ends to the middle to form a rectangle. Pass the dough back through the widest setting until the sheet is long and rectangular. Then pass it through each successive setting (1, 2, 3, etc.) until reaching the desired thickness (typically setting 6).
6. Rest the lasagna noodles. Trim the lasagna to the desired size and sprinkle each sheet with semolina (or other flour).  If using immediately, allow the noodles to dry for 10-30 minutes.
7. Par-boil (blanch) the lasagna noodles. Add the noodles 2 or 3 at a time to a large pot of boiling salted water and cook for 20 to 30 seconds. Remove them to an ice bath to stop the cooking  and dry them on a clean kitchen towel and lay them out (try not to stack them all on top of each other if possible so they don't stick together). Repeat with the remaining lasagna noodles.  

Make the Béchamel

1. Prepare the roux. In a medium-sized pot over medium heat bring the milk to almost to a boil and turn off the heat. In a second larger pot, melt the butter over medium heat. Once the butter is melted, add the flour a little at a time whisking constantly to remove any lumps. Continue whisking and stirring until the flour is cooked and the roux is light golden brown (about 3 to 4 minutes).
2. Add the hot milk. When the roux is golden brown and fragrant, turn the heat down to low and add one ladle full of hot milk whisking vigorously to incorporate it into the roux. Continue adding ladles of milk and whisking to combine until all the milk is added and the bechamel is smooth. Continue cooking and whisking for about 3 to 4 more minutes or until the bechamel thickens and coats the back of a spoon but is still easily spreadable.
3. Adjust the seasonings. Add more salt, pepper, and freshly grated nutmeg to taste. If you're not using it right away, cover the top of the sauce with sustainable cling film to keep a skin from forming.

Assemble & Bake the Lasagna Bolognese

1. Assemble the lasagna. Use a deep lasagna dish (or 9x13 baking pan)

• Spread 1/4 to 1/2 cup béchamel or ragù evenly across the bottom of the baking dish and cover with lasagna noodles slightly overlapping each other so there are no gaps.
• Add ragù and spread it out evenly across the top of the noodles, then add béchamel sauce and spread it out evenly across the top of the ragù and sprinkle with grated Parmigiano cheese.
• Add another layer of pasta, add more ragù and more Parmigiano cheese.
• Add another layer of pasta, then ragù, béchamel, and Parmigiano cheese.
• Repeat layering the ingredients in this order until there is no more ragù left. Finish the top layer with the ragù, a little béchamel, and a generous handful of grated parm for a creamy-crispy top or for a soft and creamy top, finish the lasagna with béchamel and parm. For an ultra crispy top, layer with ragù and parmigiano cheese only.

    2. Bake the lasagna. Cover the lasagna tightly with aluminum foil and bake covered in a preheated oven at 350°F/176°C for 35 to 40 minutes or until bubbling and hot. Remove the aluminum foil, turn on the broiler, and cook the lasagna under the broiler for a few more minutes, or until nicely browned. Remove from the oven and allow to cool for 10 to 20 minutes before cutting into it, Enjoy!