Portobello Burgers

INGREDIENTS

• 4 large portobello mushrooms, 5 to 6 oz. each, brushed clean and stemmed
• 1 Tbs. extra-virgin olive oil
• 4 whole-grain burger buns, split
• 2 Tbs. extra-virgin olive oil
• 1 Tbs. red wine vinegar
• 1 tsp. Dijon mustard
• 1/2 tsp. minced garlic
• 1/4 tsp. kosher salt
• Freshly ground pepper, to taste
• 1 Tbs. water
• 1 tsp. minced fresh thyme
• 1 tsp. minced fresh rosemary
• 1 tsp. minced fresh dill or flat-leaf parsley
• 5 oz. torn mixed salad greens (about 4 cups loosely packed)
• 4 thick slices beefsteak or other large tomato