Ingredients

4 portobello mushrooms, stems removed
2 tbsp balsamic vinegar
2 tbsp olive oil, divided- split in half
1 cup sliced white onion
2 oz soft goats cheese
1 on-the-vine tomato, sliced
2 cups field greens
4 tsp Dijon mustard
4 whole-wheat burger buns

Preparation

Combine first 4 ingredients in a large zip-top plastic bag; add mushrooms to bag. Seal and marinate at room temperature for 2 hours, turning bag occasionally. Remove mushrooms from bag; discard marinade.

Prepare grill to medium heat.

Grill Onions until the are brown and caramelized. Add Goat Cheese

Add Olive Oil, and place mushrooms, gill sides down, on grill rack grill 2-3 minutes on each side. Place buns, cut sides down, on grill rack coated grill 30 seconds on each side or until toasted. Spread condiments on the bun and assemble.