Preheat oven to 425⁰ F. Line a baking sheet with parchment or spray a casserole dish with cooking spray.
Clean mushrooms with a soft mushroom brush. Remove stems and place mushrooms on the prepared tray with the cavity side facing up.
With a small spoon, generously stuff the mushroom cavities with the goat cheese.
Sprinkle chopped pistachios over the top of the cheese on each mushroom
Bake at 425⁰F for approximately 10-15 minutes, or until the cheese is beginning to brown.