These stuffed mushrooms make a great starter or party snack, but they can also be paired with a salad for a filling vegetarian meal. A mix of olives and onions with a bit of hummus make up the flavorful stuffing. It’s used to fill mushrooms that are baked until tender and then finished with a sprinkle of feta cheese.
Preheat the oven to 400 degrees. Remove the stems from the mushrooms. Finely chop the stems and set aside. Use 2 tablespoons of olive oil to rub each mushroom cap. Place the mushrooms top side down in a 9-x-13-inch baking dish. Bake for 10 minutes.
Heat the remaining 2 tablespoons of olive oil in a large skillet over medium heat. Add the garlic and the chopped mushroom stems. Cook until the stems soften, about 3 minutes. Stir in the green and Kalamata olives; cook for 1 more minute. Stir in half of the red onions and cook for 1 more minute. Remove from the heat and stir in the hummus.
Use a spoon to fill each mushroom cap with an equal amount of olive-hummus mixture. Return to the oven and bake for 10 more minutes until the mushrooms are tender. Sprinkle with the remaining onion, feta cheese, and parsley before serving warm.