Steps

• First, prepare the ragù alla bolognese

  Wash the celery and carrot and peel the onion. Finely chop all the vegetables with a food processor or mezzaluna.

  

• Prepare a wide, not very tall pot with a double layer on the bottom to prevent the ragù from sticking while cooking.
   Pour the extra-virgin olive oil into the pot and add the minced vegetables, and let them sauté slowly without raising the heat.

  

• They should cook for about 8 minutes, stirring occasionally.
   Meanwhile, wash and finely chop the rosemary.
  When the vegetables are softened, raise the heat and add the diced pancetta and the meat, a little at a time, stirring.

  

• Add the chopped rosemary and let everything flavor together until the moisture has evaporated and the color has changed.

  

• Now deglaze with the red wine and continue cooking over high heat until it has completely evaporated and the meat has darkened taking color from the wine.
  

  

• Do not add the sauce if the wine has not completely evaporated because there must be no trace of alcohol, which would give the sauce an unpleasant taste.
   As soon as the wine has evaporated, add the tomato passata and the tomato paste, a couple of generous pinches of salt, a generous grind of pepper and stir.

  

• Cover and wait until it starts to simmer again.
   At this point transfer the pot to a low flame relative to its size and reduce the heat to a very low simmer.

  

• The ragù must cook for 3 hours with the lid on. Stir it occasionally with a wooden spoon. After the indicated time, taste and adjust the salt.
   For a good ragù alla bolognese, here comes the magic touch that sets it apart from other ragùs.

  

• The ragù alla bolognese, following the original recipe, is now ready to be used.

  

• This is based on béchamel, so we will make all the béchamel needed for the other preparations and then divide it.

  Above in the ingredients I divided the various quantities of béchamel needed for the different sauces; below I will give the whole procedure if you want to make it at home using 1 liter of milk.

  

• 1 liter whole milk
  100 g butter
  100 g all-purpose flour
  Half a teaspoon nutmeg
  1 teaspoon salt (level)
  pepper to taste

• The béchamel
  Pour the milk into a small saucepan, add the nutmeg and salt, and warm it up.
  Put the butter in another small saucepan and let it melt gently, then add the flour all at once, whisking vigorously by hand to prevent lumps.

  

• You will see the mixture turn golden; that is the roux. Now gradually pour the hot milk in, stirring vigorously to avoid lumps.
  Continue to stir over low heat until the béchamel reaches the desired creaminess.

  

• Once the béchamel is ready, divide it into 3 parts: one portion to mix with the pesto, two ladles for the base of the pan, and the rest for the white cheese sauce.
  Leave it in the pot and while it is still hot, add the finely grated provola and mix. Set aside.

• Now prepare the green sauce, that is, the pesto which you can buy or make following my recipe.
  Once the béchamel has cooled slightly you can mix it with the pesto.

  

• Here are the three sauces ready.

  

• In a baking pan make a layer of béchamel.
  Then a layer of lasagna sheets.

  

• Then divide the surface into three parts: one will be made with the green sauce, one with the white cheese sauce and the other with the ragù.

  

• Scatter a little mozzarella, and continue like this until you have used all the ingredients.

  

• Finally, sprinkle with Parmigiano-Reggiano.

  

• Cover the pan with a sheet of parchment paper and then a sheet of aluminum foil on top.
  Bake in a conventional oven at 356°F for 25 minutes.
  After the time has passed, let rest for 10 minutes and then serve.

  Here is the Three-color Lasagna with pesto, béchamel and ragù.