Got some really large flat mushrooms at the Tipperary Mushrooms stall in Mahon Point recently. They have various dressings available. I got chorizo and mozzarella.
They make a decent starter but don't expect too much of the dressings. The cheese was a very very thin slice and the sausage bits were minute. Still the taste was there and they went down well.
Check out my review of Tipperary Mushrooms - I am cork - on Qype