Heat oven to 425 degrees (or 400 convection). Place the trimmed brussel sprouts in a 9X13 baking dish in a single layer. Toss the brussels with 2 Tbsp of melted butter, 3/4 tsp salt and several grinds of pepper. Spread evenly in the dish, cover tightly with foil wrap, and place in oven. Roast for 15 minutes then remove foil and stir. Continue to roast uncovered, stirring once or twice, until they are very well browned and pierce easily with a knife, about 15 more minutes.
While the brussels roast, in a small bowl combine the last 1 Tbsp melted butter with the breadcrumbs and gruyere cheese. Add a pinch of salt and pepper and stir together.
When the brussel sprouts are tender and browned , remove from oven. Whisk together the cream, garlic powder, onion powder and cayenne. Slowly pour the cream mixture over the brussels (they will not be totally covered). Return pan to oven and roast for 5 minutes until cream is bubbling and a saucy consistency.
Remove pan from oven and turn oven to broil. Sprinkle breadcrumb mixture on top of brussels and return to oven, broiling for about 3-4 minutes until top starts to brown. Serve hot.
Enjoy!