How to Make It
In a small bowl, whisk the mayonnaise with the lemon zest and juice and whisk in the olive oil until smooth. Season the dressing with salt and pepper.
In a large skillet, heat the vegetable oil. Add the sliced shiitake and season with salt and pepper. Cover and cook over moderate heat, stirring a few times, until tender and browned, about 8 minutes. Transfer to a plate and let cool to room temperature.
In a large bowl, toss the arugula with the mushrooms and mint. Pour the dressing over the salad, toss well and serve.