These mushrooms are so meaty, you won't believe they're not, well, meat! They're also great to stuff in sandwiches, burritos, tacos or enchiladas.
Technique tip: If you don't have a grill, the broiler is just fine. Either way, be sure to brush or drizzle the mushrooms with more oil if they start to look too dry.
Swap option: Instead of the portobellos, remove the stems from 1 pound shiitake mushrooms. Thread the mushroom caps on metal skewers or wooden ones that have been soaked in water for at least 20 minutes. Proceed with the recipe from the beginning of Step 1. It's a little more work but still makes one impressive dish.
For the soy vinaigrette:
Put all ingredients in a blender and turn the machine on; a creamy emulsion will form within 30 seconds. Taste and add more vinegar, a teaspoon or 2 at a time, until the balance tastes right to you.
For the mushrooms:
Heat a charcoal or gas grill or turn on the broiler for medium heat. Adjust the rack 4 to 6 inches from the heat source. Rub or brush the mushrooms with enough oil to lightly coat them, and then sprinkle liberally with salt and pepper.
Grill or broil until they shrink and are lightly browned and slightly crisp, anywhere from 2 to 5 minutes per side, depending on your equipment. Brush or drizzle them with more oil if they start to look too dry. Transfer to a cutting board and cut into thick ribbons.
For the salad:
Put the greens in a large bowl and toss with 1/4 cup of the dressing. Spread the mushroom slices on top and drizzle with their accumulated juices. Drizzle with a little more of the dressing and serve.