Bring a large pot of water to a boil. Add a pinch of salt and the Brussels sprouts. Boil for 8 to 10 minutes until they are tender. Drain immediately and plunge into an ice bath. Pat thoroughly dry with paper towels.

Place the dried sprouts on a lightly oiled baking sheet. Use the bottom of a glass or jar to gently press each sprout until it flattens to about 1/2-inch thick.

Drizzle the sprouts with olive oil and sprinkle with garlic powder, onion powder, salt, black pepper, and cayenne pepper if desired. Roast in a preheated 425°F oven for 20 to 30 minutes until the edges are crisp.

If using Parmesan, sprinkle it on the sprouts during the last 5 minutes of roasting to let it melt slightly. Remove from the oven and serve warm.