Preheat oven to 350 degrees.
In large skillet, heat butter over medium-high heat. Add mushrooms; cook 8–10 minutes, or until deep golden brown, stirring frequently. Season with salt and pepper; remove from heat.
Place brie on parchment-lined, rimmed baking pan; drizzle with honey. Transfer to oven and bake 5–7 minutes, or until inside of cheese is softened but outside remains intact.
Transfer brie to serving platter; top with pomegranate arils, pistachios and the cooked mushrooms. Serve with crackers or bread.