Parmigiano-Stuffed Mushrooms

Finely ground Parmigiano-Reggiano adds great texture (and flavor) to the stuffing in these savory, three-bite appetizers.

• 
  
  2 oz. (4 Tbs.) unsalted butter
  
  


• 
  
  24 large white button mushrooms (about 2-1/2 inches wide; 2-1/2 lb. total), stemmed; stems finely chopped and caps wiped clean
  
  


• 
  
  Kosher salt
  
  


• 
  
  3 oz. Parmigiano-Reggiano, finely ground in a food processor (3/4 cup)
  
  


• 
  
  3/4 cup plain panko
  
  


• 
  
  1/3 cup mayonnaise
  
  


• 
  
  1/4 cup finely chopped fresh flat-leaf parsley
  
  


• 
  
  Freshly ground black pepper
  
  


• 
  
  1-1/2 Tbs. extra-virgin olive oil
  
  

Position a rack in the center of the oven and heat the oven to 400°F.

Melt the butter in a 10-inch nonstick skillet over medium heat. Set aside 2 Tbs. of the melted butter in a small bowl. Add the mushroom stems and 1/4 tsp. salt to the skillet and cook, stirring often with a wooden spatula, until tender, about 5 minutes. Let cool to room temperature.

Meanwhile, add 2 Tbs. of the Parmigiano and the panko to the reserved melted butter and mix thoroughly; set aside.

In a medium bowl, stir together the remaining Parmigiano, the mayonnaise, parsley, and 1/4 tsp. black pepper. Add the mushroom stems and mix until well combined.

In a large bowl, toss the mushroom caps with the oil. Fill each mushroom cap with a rounded teaspoon of the filling and top each with about 1 tsp. of the panko mixture. Place on a large rimmed baking sheet with space in between. Bake until tender and the topping is golden-brown, about 25 minutes. Cool briefly before serving.