Cook trout gratin according to package instructions. Drizzle butternut, pumpkin & sweet potato with olive oil and season with sea salt. Roast at 200°C for 20 minutes or until cooked through. Melt butter in a pan over medium heat. Let it foam and go nutty golden brown. Add sage leaves and fry for 30–60 seconds until crisp. Spoon immediately over the roasted veg just before serving. Serve trout gratin with roasted veg and enjoy