"Preheat oven to 425F degrees. Arrange rack into the upper third position of the oven.In a microwave safe bowl, parboil brussels with 2 tablespoons water for 5-6 minutes on high, or until nearly fork tender (stirring and rotating halfway through). Drain and thoroughly pat dry. Meanwhile, in a small saucepan, combine butter and 2 whole garlic cloves and simmer on low until butter is melted and garlic has infused its flavor. Keep the butter and garlic on warm until needed. Transfer brussels to a large, rimmed baking sheet. Using the flat bottom of a large glass or mug, smash the brussels into ½-inch thick disks. With a pastry brush or small spoon, drizzle each sprout with the garlic-infused butter, leaving half of the butter for the other side. Season to taste with sea salt, black pepper, and red pepper flakes, if using. Bake for 15 minutes, then flip. Using remaining butter, brush alternate sides. Sprinkle with Parmesan and continue baking until crispy and cheese is golden brown, about 5-10 minutes.Garnish with lemon zest, if desired, and serve immediately for maximum crispness. "