Wash brussels sprouts, trim the bottom and remove any outside leaves that are discolored or spotted.
In a large saucepan, bring about half a pot of water to a boil then add the brussels sprouts. You only need enough water to cover them. Cook about ten minutes or until fork-tender.
When brussels sprouts are done remove them from the pot and drain in a colander. Dry them with a paper towel.
If cooking in a regular oven, preheat your oven to 425 degrees.
Place brussel sprouts in a medium size bowl with the olive oil, garlic salt, pepper and chili flakes and stir to coat. Roll each brussel sprout in parmesan cheese. If baking in the oven don't roll in the parmesan cheese. You will roast them for 15 minutes and then sprinkle the cheese on and return to the oven for 5-10 minutes to melt it.
Place the brussels sprouts on the air fryer pan or on a baking sheet. Using a heavy glass smash each one to flatten it out.
If using an air fryer bake at 375 degrees for 7-8 minutes or until the brussels sprouts are golden brown.
If using a regular oven bake at 425 degrees for 15 minutes. Remove from the oven and turn with a spatula or tongs. Sprinkle the parmesan on the top and return to the oven for 5-10 minutes until the cheese is melted and the brussels sprouts are golden brown.
With both methods watch the brussels sprouts closely for doneness.