In a pot sauté pork neck, veal and Italian sausage with 100 gr of butter, olive oil and seasoning until cooked through. Remove from the heat and allow to cool to room temperature.
In a fry pan sauté celery, onion and three cloves of minced garlic until tender. Remove from the heat, allow to cool slightly and add to the pork neck, veal and Italian sausage.
Put all of the above plus the Mortadella through a mincer with a thin wheel attachment 3 times.
In a pan heat 100g butter until it foams. Add 1 bunch of sage leaves and the leftover cloves of garlic and cook until butter browns.
Once meat mixture is well combined stir through the parmesan, chopped parsley, eggs, seasoning, nutmeg, and burnt butter sauce to make a smooth stuffing. Refrigerate for 2 hours or until cool.
Roll the pasta through a pasta machine until you obtain a very thin sheet. Cut it in with a 7cm round cutter.
Place around 4g of stuffing in the middle of each circle piece of pasta. Baste a small amount of water onto each piece of pasta and close into a semi-circle shape. Seal the edges well and squeeze out all air to get a tight seal.
Cook the casoncelli in plenty of boiling water with about 10g of salt per litre for about 4 minutes
Serve them with burnt butter and sage sauce (see step 4), parmesan and crispy guanciale