Pre-cook the conchiglie in salted water and quench so that they are still fairly firm to the bite.
Tomato sauce:
Fry the cubes of bacon in 1 tablespoon of olive oil. After a while, add the chilli rings and onion cubes and let them become translucent. Add the tomato paste, lightly toast, deglaze with white wine and reduce. Then add the tomatoes and season with sugar, salt and pepper. Let it reduce and finally add the balsamic vinegar and olive oil.
Béchamel:
Make a roux with the butter and flour. Over a low heat, stirring constantly, add the vegetable stock until it is used up. Do the same with the milk. Cook slowly, stirring, until the consistency becomes creamy. Stir in the grated cheese (e.g. Gruyère, Emmentaler, Gouda) and continue cooking on the lowest heat for approx. 1 minute until the cheese has dissolved. Season to taste with salt, pepper and nutmeg.
Preheat the oven to 175 ° upper-lower heat.
Filling:
Mix the ricotta with the peas, egg and parmesan well. Season to taste with oregano, salt and pepper.
Fill the conchiglie with the ricotta mixture and place with the open side up in an ovenproof baking dish (approx. 30 cm). First pour the tomato sauce over it, then the bechamel sauce and finally sprinkle with grated cheese (you can replace part of this with buffalo mozzarella). Slide the casserole dish onto a grid in the 2nd rail from the bottom of the oven and bake for approx. 45 minutes.