This sure comes close. The vegetarian 'Shroom Burger (USD 6.99) from the famous Shake Shack features a glorious deep fried portobello mushroom as its main ingredient.
Accompanied by trusty companions Patrick and Sandy — I mean, the fresh slice of tomato and lettuce, it makes for a gastronomical experience. Now, if only they would come to Singapore!
Oh, did I mention that the portobello mushroom is stuffed with melted cheddar cheese?