1. Balsamic Glaze: Combine vinegar with sugar and salt in a small saucepan set over medium. Stir until sugar dissolves. Gently boil until glaze is reduced to 1/4 cup and coats the back of a spoon, 3 to 5 min. Set aside.

2. Discard stem and scrape out and discard brown gills from mushrooms, then pierce each a few times with a fork. Reserve 2 tbsp balsamic glaze, then brush remaining glaze over mushrooms and zucchini. Let stand on a baking sheet for 10 min.

3. Preheat barbecue to medium-high. Oil grill. Arrange mushrooms, stem-side down, and zucchini slices on grill. Cook, lid closed, 6 to 8 min for mushrooms and 3 to 4 min for zucchini.

4. Flip mushrooms and divide cheese among 4 of the mush- rooms. Reduce heat to medium. Transfer zucchini to a platter. Continue cooking mushrooms, lid closed, until cheese is melted, about 2 min. Reserve 2 unstuffed mushrooms and half of zucchini for Mushroom, Zucchini & Tomato Pasta Salad.

5. Slice remaining zucchini into 1-in. pieces. Whisk reserved 2 tbsp balsamic glaze with 2 tbsp oil and salt in a large bowl. Add spring mix and zucchini, and toss until coated. Divide salad among 4 plates and top each with 1 stuffed mushroom. Toss tomatoes with basil and remaining 1 tbsp oil. Top mushrooms with tomato mixture, then season with pepper.