Portobello Steak Burger

A portobello burger fails when the cap is treated as a patty-shaped object and simply grilled until limp.

The trick is driving the water out under real heat so the mushroom concentrates rather than steams.

The marinade doubles as a basting liquid; reduce whatever is left in the pan and spoon it over.

Caramelized onions can be made days ahead and are worth making in quantity.