I have had the 'bello wit the sauce Ingredients
2 oz (50 g) mature Cheddar, grated
1 oz (25 g) Parmesan (Parmigiano Reggiano), finely grated
1 pint (570 ml) milk
1½ oz (40 g) plain flour
1½ oz (40 g) butter
pinch of cayenne pepper
a little freshly grated nutmeg
salt and freshly milled black pepper....
But always as My own dish...I wanted to have the same taste individually...in small food stations...
Try it it is so good! you can also put the portobello with pam on a tray and make a pesto (olive oil, basil, sea salt, black pepper) put it as a first layer , the chop some sundried tomatos, and mozzarela on top and broil... Even kids love them!