Spinach pasta:
Put all the ingredients in the food processor bowl and mix for 30 seconds using the steel blade.
Add water if necessary.

Place the ball of dough on a plate. Drizzle with a little olive oil and smooth.
Cover the plate with a towel and let rest for 15 to 20 minutes.

Cut a 1/2″ (1 cm) thick slice of dough.
Flatten with your hands.
Put the machine at the first hole (the largest).
Pass the slice through the rollers.
Fold the slice and pass it again. Repeat this step 5 to 7 times until the dough is smooth.
Sprinkle the slice with semolina regularly.
Put the machine at the 2nd and 3rd hole, repeat the previous step once.
The 4th and 5th holes will flatten the sheet enormously.
Stop at the 5th hole for tagliatelle, ravioli, and fettuccine.
Stop at the 6th hole for lasagna and cannelloni.

Bechamel:
In a medium saucepan, melt the butter over medium-low heat.
Add the flour and mix with a whisk until smooth, then stir, without stopping, for about 3 minutes.
Add the milk, a little at a time, and mix until smooth.
Cook, stirring, for about 5 minutes, or until the sauce thickens.
Season with salt, pepper, and a pinch of nutmeg.

Meat sauce:
Preheat the oven to 350 F (180 C)
Heat the olive oil in a large pot over medium-high heat.
Add the chopped pancetta, onion, and celery, and cook, stirring often with a wooden spoon, for 10 minutes, or until the onions start to color.
Add the 3 meats and prosciutto and cook for 15 minutes, or until the meats are well browned.
Reserve the contents in a plate, having previously drained the fat.

In the same pot, add the wine to deglaze the cooking juices and reduce by half.
Return the meat to the pot.
Add the chicken broth, 1/2 cup (125 ml) at a time, allowing it to reduce between each addition.
Add the milk, then the rest of the ingredients, and cover.
Put in the oven for 5 hours, stirring occasionally.
The last hour of cooking, cook uncovered.
Season to taste with salt and pepper.

Assembly:
Spread 1/3 of the bechamel in the bottom of a 9″ x 13″ (23 cm x 33 cm) rectangular dish
Place a layer of pasta, then cover with meat sauce.
Sprinkle with 1/3 of the cheese.
Repeat the operation once more, finishing with a layer of pasta, covered with the last 1/3 of bechamel and cheese.
Bake in the oven for 1 hour, or until the top is golden brown.