For the bolognese sauce (make one day ahead):

1. Heat your Dutch oven on the stove over medium-high heat. Add in olive oil. Once the oil is hot enough, add in carrots, onion, celery, whole smashed garlic cloves, salt, pepper, and red pepper flakes. Stir frequently until onions are translucent.
2. Add in ground beef and ground pork. Season the meat with salt and pepper. Stir and break up the meat into small chunks.
3. When the meat is lightly browned, add in tomato paste, continue stirring, and cook the tomato paste down for two minutes.
4. Add in wine. Stir in and scrape up all the browned bits from the Dutch oven. Let the alcohol evaporate for two minutes. 
5. Next, stir in San Marzano tomatoes, beef broth, and cheese rind. Season more with salt, pepper, and red hot pepper flakes.
6. Bring to a boil, lower the heat, cover, and simmer for 3 hours.
7. Remove the cheese rind and whole garlic cloves.
8. Stir in the balsamic vinegar, sugar, and black truffle oil. Season with more salt and pepper to taste.

For the fresh pasta sheets:

1. In your mixer bowl, add in the “00” flour and create a well in the middle with your hand. Crack eggs into the well, along with salt and extra virgin olive oil.
2. Attach the paddle to your mixer and set it to the lowest speed. Mix until the ingredients incorporate and the dough comes together into small, sticky clumps.
3. Gently knead the dough with your hands for about 10 minutes, until smooth. Add flour to your work surface as needed, to ensure your dough does not stick.
4. Form the dough into a ball and wrap it tightly in plastic wrap. Place in the refrigerator to chill for 15 minutes.
5. Remove the dough from the refrigerator and cut it into three even pieces.
6. Replace the mixer paddle with the pasta roller. Set the mixer to the lowest speed. Run each piece of dough through the pasta roller. Start with setting #1 (the widest setting) and continue the process through setting #8 (the thinnest setting), until you’ve rolled out all the dough into pasta sheets for lasagna.
7. Later, you may need to cut the sheets to fit properly in the pan. 

For the ricotta-spinach filling:

1. Defrost frozen spinach, and squeeze all of the excess water from the spinach with your hands.
2. In a bowl, mix together the ricotta, spinach, parmesan, egg, nutmeg, and black pepper, and set it aside. 

For the béchamel sauce:

1. In a pan over medium heat, melt the butter completely, then whisk in the flour. Continue whisking vigorously for one minute to cook the flour. 
2. Add in a small splash of milk, and whisk. Continue adding in milk, a little at a time, whisking all the while. If any lumps form, just keep whisking. The sauce should become thick.
3. Bring the sauce to a low boil, and continue whisking for 2-3 minutes.
4. Stir in the mozzarella cheese, allowing it to melt. Turn off the stove. 

To make the lasagna:

1. Preheat the oven to 350 degrees.
2. In a lasagna baking dish, smooth a small spoonful of bolognese sauce over the bottom of the pan. 
3. Add one layer of pasta sheets. Smooth a thin layer of the ricotta-spinach mixture on top. Add a sprinkling of mozzarella cheese. Cover the cheese with bolognese sauce.
4. Repeat this pattern until the pan is almost full to the top, ending with the bolognese sauce. Re-whisk the béchamel sauce and pour it over the top of the lasagna. Sprinkle on a bit more mozzarella. 
5. Bake for about 40 minutes, uncovered, until the top of the lasagna is bubbling and golden-brown.
6. Allow the lasagna to set and cool down for at least 20 minutes before digging in. Enjoy!