Step 1

Position racks in upper and lower thirds of oven; preheat to 475°F.

Step 2

Wipe mushrooms clean and trim stems flush with caps. Score a 1/4-inch X across the cap of each mushroom. Toss the mushrooms, oil, 1/4 teaspoon salt and pepper together in a large bowl until the oil is absorbed. Arrange the mushrooms on a large rimmed baking sheet. Roast on the lower rack until browned and very soft, about 20 minutes.

Step 3

Meanwhile, chop parsley. Add lemon zest, garlic and the remaining 1/4 teaspoon salt to the parsley on the cutting board and continue chopping until finely chopped.

Step 4

When the mushrooms are done, remove them from the oven and turn the broiler to high. Turn the mushrooms stem-side up on the pan and use the bottom of a mason jar or other sturdy glass to flatten each mushroom. Broil on the upper rack until crisp on the bottom and edges, 3 to 4 minutes. Serve topped with the gremolata.