Once upon a time at Urban Burger there was a delightful vegetarian burger called Port Melbourne. Sadly it’s out of commission now, but based on its principles I’d probably reconstruct it like this:
Panini roll or other kind of awesome roll toasted and slathered with butter or herb mayo or even pesto.
One huge field mushroom, grilled to the point of collapse (in garlic oil or some other such delightful heart attack inducing goodness, garlic butter?!).
Sundried tomatoes, artichokes, roast capsicum.
Buffalo mozzarella.
Tomato relish or maybe even some crazy flavoured chutney.
