Makes 19 stuffed mushrooms
19 small button mushrooms, stems removed and minced
1 tablespoon olive oil, plus extra
½ cup fontina or provolone cheese, divided
¼ cup Pecorino Romano
¼ cup breadcrumbs
1 medium garlic clove, minced
Place oven rack in middle position and preheat oven to 400 degrees.
In small saucepan, heat 1 tablespoon olive oil and minced mushroom stems over medium heat. Cook, stirring occasionally, until stems are soft and golden-brown, about 6 minutes. Transfer to medium bowl. Add ¼ cup fontina, Pecorino Romano, breadcrumbs, and garlic. If filling feels dry, stir in another teaspoon olive oil.
Drizzle oil lightly over each well of EZ-Melter so that each has about ¼ teaspoon oil in it. Place one mushroom cap upside down in each well of EZ-Melter. Distribute filling evenly into mushroom caps. Sprinkle remaining ¼ cup fontina over tops of mushrooms.
Bake until cheese is melted and mushrooms are soft, 15 to 20 minutes. Transfer EZ-Melter to trivet and serve immediately, using small utensils or toothpicks to remove mushrooms.