Wash the lettuce, chop the onions and cut sweetcorn into pieces.
Put mince and onions with a little salt to taste on a moderate heat in a thick bottomed pan with no fat added. PIedmontese is very lean, but it can still take the beginning of browning. Use a wooden spoon to separate the mince in the pan as it browns.
Mushrooms can be cooked separately or added to the onions and mince in the pan. I cook them separately in a small pan.
When the mince is browned, add just enough boiled water to give a couple of mm depth and let the water finish cooking the mince. If you need to top up, add just a little at a time. Let it simmer for 10 minutes and add a carton (400g) of tomato passata. Allow the mixture to simmer. If it gets too thick, just add a couple of tablespoons to the pan.
Heat up the tortilla wraps, and serve in bowls for everyone to help themselves from.