Preheat oven to 400 degrees F. Grease a large rimmed baking sheet with cooking spray.
Toss 1 lb. Brussels sprouts (including any loose leaves that have fallen off) with 3 Tbsp. oil, 2 cloves minced garlic, 1 tsp. kosher salt, and fresh cracked pepper in a large mixing bowl until coated.
Add 1/2 oz. parmesan and 1/3 c. panko bread crumbs and mix until evenly coated.
Spread Brussels out on baking sheet. (Press or sprinkle excess parmesan mixture onto the sprouts.) Bake for 20-24 minutes until golden and tender.