Step 1

Preheat oven to 400 degrees F.

Step 2

Heat 2 tablespoons oil in a large skillet over medium heat. Add scallions and garlic; cook, stirring, until softened, about 3 minutes. Remove from heat and stir in spinach, 1/2 cup feta, dill, pepper and salt.

Step 3

Brush mushrooms all over with the remaining 1 tablespoon oil. Place on a baking sheet and divide the spinach mixture among the mushrooms. Bake until hot and starting to brown, 15 to 20 minutes. Sprinkle with the remaining 1 tablespoon feta and with crushed red pepper, if desired, and serve.