How to Make It
In a large skillet, heat 1 tablespoon of the olive oil until shimmering. Add half of the mushroom slices in a single layer and cook, turning once, until golden, about 6 minutes. Drain the mushrooms on paper towels and season them with salt and pepper. Repeat with the remaining 1 tablespoon of olive oil and mushrooms.
In a small bowl, combine the mayonnaise with the 2 tablespoons of shredded basil and season with salt and pepper. Spread 1 tablespoon of the basil mayonnaise on each slice of bread and top with lettuce. Arrange the sliced tomato on the lettuce, followed by the mushrooms. Sprinkle the sandwiches with salt and pepper and garnish with basil. Serve the sandwiches open-face or close the sandwiches and serve.
King oyster mushrooms are available at farmers’ markets and specialty shops.