Grilled Portobello Mushrooms4 large portobello mushrooms 2 tablespoons pine nuts(8-10 ounces each) 1/2 cup plus 2 tablespoons balsamic vinegar2 large cloves of garlic, cut into slivers 1/2 teaspoon coarse salt1 ounce Romano, Parmigiano-Reggiano, or other firm cheese, cut into slivers 1/2 teaspoon black pepper1 sprig fresh rosemary, leaves stripped off 1 1/3 cups extra-virgin olive oil,the stem, or 2 teaspoons dried rosemary or more as needed 12 fresh basil leaves, thinly sliveredPART 1: Marinade PrepCombine 1/2 cup of vinegar and the salt and pepper in a nonreactive mixing bowl and whisk until the salt is dissolved. Whisk in the oil and the basil.Pour some of the mixture in the bottom of a nonreactive baking dish setting this aside and keeping the remaining marinade in reserve.PART 2: `Shroom PrepUsing a paring knife cut the stems off the `shrooms so they are flush with the caps.Wipe the `shrooms clean with a damp paper towel. DONT put the `shrooms under running water lest they become soggy. Use a sharp object, such as the tip of a metal skewer or a tapered chopstick or a magic dagger, to make a series of small holes in the gill side of the `shroom caps, 1/2 inch apart. Insert garlic and cheese slivers,rosemary leaves, and pine nuts in these holes.Arrange the `shrooms (gill side up) in the baking dish from Part 1. Swish the `shrooms around to coat the bottoms with marinade. Spoon the remaining marinade over the `shrooms and let them marinate in the `fridge (covered) for 30 min to 3 hrs.PART 4: Fire it upSet up the grill for direct grilling and preheat to high.When ready to cook,remove the `shrooms from the marinade. Strain the marinade if the basil looks wilted. Whisk the remaining 2 tablespoons of vinegar into the reserved marinade.Arrange the `shrooms on the hot grate, gill side down. Grill for 3 min, then invert the `shrooms and spoon in some of the reserved marinade. Continue grilling until the caps are browned and very tender, 4-6 min, rotating the caps 45 degrees after 2 min to create an attractive crosshatch or grill marks. If the caps brown too much, reduce the heat or move the `shrooms to a cooler part of the grill. Transfer to plates or a platter and serve at once.