• 1 bunch rosemary sprigs
• 8 medium portobello mushrooms , stems removed
• 1/4 cup balsamic vinegar
• Olive oil cooking spray
• 1/4 teaspoon salt
• 1/8 teaspoon freshly ground pepper
• 1 tablespoon extra-virgin olive oil

Preheat oven to 400°F. On 2 jelly-roll pans, make 2 parallel rows of rosemary sprigs.

Remove gills (black undersides) of mushrooms by gently scraping with a teaspoon. On a sheet of waxed paper, sprinkle mushrooms with vinegar; let stand until vinegar is absorbed, turning mushrooms once. Lightly spray them with cooking spray and season with salt and pepper. Arrange 4 mushrooms on each pan on top of rosemary sprigs.

Roast mushrooms about 5 minutes. Turn them over and roast until tender, about 5 minutes longer. Arrange them and rosemary on a warm platter; brush with olive oil. Drizzle with any cooking juices remaining in the pans.