For the bechamel:
°1⁄2 liter milk
°2 large tbsp of flour
°lasagna noodles (without pre-cooking)
°600 g Bolognese sauce (ready-made like Panzani)
°100 g of grated cheese
°350g minced meat
Cutting onion into small pieces & sauté in olive oil.
When the onions have browned well, add the 350g of ground beef.
Cook over medium heat then add the bolognese sauce.
Prepare the béchamel. Melt the butter over high heat.
Once melted, add the two tablespoons of flour and stir with a whisk over medium heat.
When the mixture is homogeneous (very fast), gradually add the milk, whisking constantly to avoid lumps.
Continue to stir until the bechamel thickens.
Mix the Bolognese sauce made previously with the béchamel.
Then in a gratin dish, pour a layer of this preparation then cover with lasagna dough. Repeat the same thing until the sauce is used up (about twice).
The last layer should be a sauce layer. Add the grated Gruyère and cook for around 45 min at 180° (th.6).
To know if the lasagna is cooked, prick with a knife, the lasagna noodles must be melting, so the knife must sink in without any problem.