Source: BBQ USA by Steven Raichlen (Workman Publishing, 2003)
6 large Portobello mushrooms (each 4 to 6 inches across, 8 to 10
Using a paring knife, trim the stems off the Portobellos. Wipe the caps clean with a damp paper towel. Using a sharp object, such as the tip of a metal skewer, make a series of holes in the gill side of the mushrooms, about 1 inch apart. Insert the garlic slivers into these holes, dividing them evenly among the 6 mushrooms.
Combine the mustard, steak sauce, Worcestershire sauce, barbecue sauce, vinegar, liquid smoke, salt and pepper in a mixing bowl and whisk until the salt dissolves. Whisk in the olive oil and basil. Pour one-third of the mixture in the bottom of a nonreactive baking dish and place the mushrooms in it, gill side up. Swish the mushrooms around to coat the bottoms with marinade. Spoon the remaining marinade over the mushrooms. Let them marinate for 1 to 2 hours.
Set up the grill for direct grilling using a two-zone fire. Preheat one zone to high, and the other zone to medium so you can move the mushrooms over if they start to burn.
When ready to cook, drain the mushrooms over a small nonreactive bowl to reserve the remaining marinade. Place the Portobellos on the hot grate, gill side down, and grill for about 3 minutes. Turn the mushrooms over and spoon 1 tablespoon of the reserved marinade into each cap. Continue grilling until the Portobellos are browned and very tender, about 4 minutes more. The mushrooms are done when they can be easily pierced with a skewer. If they start to brown too much before they become tender, move them over the medium zone of the grill. After the mushrooms have grilled for 2 minutes on the second side, place a slice of cheese on each and cover the grill to melt the cheese. Lightly toast the hamburger buns on the grill, 1 to 2 minutes.
To serve, place each grilled Portobello on a hamburger bun. Garnish with tomato and onion slices, and/or lettuce, if using, and the condiment of your choice.
© 2006 Steven Raichlen | site design Benjamin Wilchfort