First, adjust your oven racks to the center and upper third positions, and preheat your oven to 425 degrees F. This high heat will help to achieve that beautiful crispiness we’re after.
Next, take a large saucepan and fill it with enough water to comfortably accommodate the Brussels sprouts. Bring it to a rolling boil. Once boiling, remember to add 2 teaspoons of kosher salt to enhance the flavor of the sprouts.
While waiting for the water to boil, prepare an ice bath by filling a large bowl with ice and water. This will stop the cooking process once the sprouts are boiled.
Now, add the trimmed Brussels sprouts to the boiling salted water. Let them cook for about 10 minutes, or until they are fork-tender. This boiling method helps prepare them for smashing.
Once cooked, carefully drain the Brussels sprouts and immediately plunge them into the ice bath. This step is crucial to maintain their vibrant green color and stop the cooking.
Let the sprouts cool in the ice bath for about 1 minute, then remove them and place them on a layer of paper towels. Gently pat them dry to remove excess moisture.
Transfer the cooled Brussels sprouts to the center of a large, rimmed baking sheet. Drizzle them with 2 tablespoons of olive oil, and sprinkle the remaining ½ teaspoon of kosher salt, ground pepper, and red pepper flakes if using. Toss everything together until well-coated.
Now comes the fun part! Using the base of a drinking glass or coffee mug, gently but firmly press down on each sprout to flatten it into a disk that's about half an inch thick. This technique helps maximize the crispy edges.
Place the baking sheet in the preheated oven and bake the Smashed Brussels Sprouts for 15 minutes. After this, carefully flip each sprout over.
Sprinkle the grated Parmesan generously over the top of the sprouts and return them to the oven. Bake for an additional 5 to 10 minutes until they are golden brown and crispy on the outside.
If you prefer an extra crispy top, you can transfer the pan to the upper rack and switch the oven to broil. Keep a close eye on them, broiling for just 2 to 3 minutes until they reach your desired crispiness.
Finally, remove the Smashed Brussels Sprouts from the oven and, if using, squeeze some fresh lemon juice over the top for a refreshing finish. Serve them hot and enjoy!
