2largeportobello mushrooms (each about 4 inches in diameter)
kosher salt and freshly ground black pepper
2whole-grain hamburger buns, split
4Roma tomato slices
2slicesfresh goat cheese
1/2 cup fresh baby spinach leaves
Remove the stems from the mushrooms and discard. Use a spoon to scrape the gills from the caps and discard. Lightly brush both sides of the mushrooms with 1 tablespoon of the olive oil. Season with salt and pepper to taste. Set the mushrooms on the broiling pan, cap side up.
Turn on Broil/Grill function. Cook for 10 minutes, or until the mushrooms tender.
While the mushrooms are cooking, place the mayonnaise and pesto in a small bowl and stir until well combined.
Remove the mushrooms from the oven.
Place the split buns, cut side up, on the crisper tray, turn on Toast function and toast on level 4.
To assemble the sandwich, spread 1 heaping tablespoon of the pesto mayonnaise on the bottom of each bun. Place the mushroom on the bun. Top each portobello with 2 tomato slices, 2 slices of goat cheese, and a small handful of spinach leaves. Finish with the top of the bun.Serve warm.