Mushrooms with Soy Butter

Preparation

1. Step 1

   Finely chop scallion to measure 1 Tbsp. Process butter and soy sauce in a food processor, scraping down sides frequently, until smooth and well blended. Transfer to a small bowl; stir in chopped scallion. Season soy-scallion butter with salt and pepper.

   Step 2

   Place mushrooms in a large bowl. Thinly slice remaining scallions on a sharp diagonal. Set aside 1/4 cup scallions for garnish; add remaining scallions to mushrooms. Drizzle with oil, season with salt and pepper, and toss to coat.

   Step 3

   Place two 18x12-inch sheets of parchment paper, or heavy-duty foil if grilling, on a work surface. Divide mushrooms evenly on one half of each sheet; dot each with 4 Tbsp. soy-scallion butter. Fold foil over mixture and crimp 3 edges tightly to form a sealed packet. DO AHEAD: Packets can be made 4 hours ahead. Chill. Let stand at room temperature for 15 minutes before continuing.

   Step 4

   Preheat oven to 425°. Arrange packets in a single layer on a rimmed baking sheet. Alternatively, build a medium-hot fire in a charcoal grill, or heat a gas grill to high. Bake or grill packets until mushrooms are tender (carefully open 1 packet to check; steam will escape), about 15 minutes. Carefully cut open packets. Dot each with remaining soy-scallion butter. Garnish with sliced scallions.