melt butter in a pan large enough to fit all ingredients over med-high heat; add onions

sauté onions until soft and translucent, then add garlic and sauté for about 1-2 minutes or until garlic becomes aromatic

place brussel sprouts cut-side down into the pan and sprinkle with salt and pepper

allow brussel sprouts to cook for 4-6 minutes per side, turning once

Remove pan from heat and add parmesan cheese