Boil or Steam Until Tender: Bring a large pot of salted water to a rolling boil. Add trimmed Brussels sprouts and boil for 8 to 10 minutes until easily pierced through the core with a fork or knife tip. Drain thoroughly in a colander and let steam dry on a clean kitchen towel for 5 minutes. Getting them dry is the secret to extreme crispiness!

Prep the Pan with Garlic Parmesan Bed: Preheat oven to 425°F (220°C). Drizzle 1 tablespoon of olive oil and melted butter across a large heavy rimmed baking sheet. Scatter minced garlic and half of the grated Parmigiano-Reggiano (1/2 cup) evenly over the surface.

Smash the Sprouts: Place the steamed Brussels sprouts onto the prepared baking sheet, leaving space between them. Using the flat bottom of a heavy drinking glass, mason jar, or measuring cup, press firmly straight down on each sprout until flattened into a thin disc with shattered, lacy edges.

Season & Top: Drizzle the tops with the remaining 2 tablespoons of olive oil. Season evenly with garlic powder, onion powder, kosher salt, black pepper, and red pepper flakes. Shower the tops with the remaining 1/2 cup of grated Parmigiano-Reggiano cheese.

Roast to Ultra-Crispy Perfection: Roast at 425°F for 20 to 25 minutes, until the bottom forms a crispy golden-brown cheese frico skirt and the ruffled top leaves turn deeply caramelized and shatteringly crisp. Broil for 1 to 2 minutes if extra char is desired.

Drizzle & Serve: Transfer the crispy smashed sprouts onto a warm serving platter. Drizzle generously with glossy balsamic glaze reduction, sprinkle with flaky sea salt and fresh thyme leaves, and serve hot straight from the oven!