Heat a frying pan over medium heat until hot, 3 minutes. Melt 1 tablespoon butter; cook and stir garlic until fragrant, 30 seconds. Add 1 tablespoon butter and Brussels sprouts, cut-side down; cover and cook until golden brown, 4 to 6 minutes.
Flip Brussels sprouts; add 1 tablespoon butter. Cover and cook until other side is browned, about 3 more minutes. Transfer to a serving plate. Sprinkle with Parmesan cheese, salt, and black pepper.