In a small nonstick skillet, heat a drizzle of oil. Add mushrooms and saute until tender 5-6 minutes. Season with a pinch of salt and pepper (can double this amount if you want leftovers).
Bake or cook veggie burger patty on stove top per package instructions. In the last minute add a slice of cheese to melt.
Meanwhile place all salad ingredients in a large serving bowl (salad greens through pickles). Drizzle with dressing of choice. Top with veggie burger patty, mustard and ketchup.
Recipe by Nutritious Eats at https://www.nutritiouseats.com/veggie-burger-salad/