Wild Mushroom Frittata

I swear that someday I will host a brunch event. I really need to get on that.

Wild Mushroom Frittata
Serves 4
1 tablespoon extra-virgin olive oil
2 teaspoons butter
3/4 pound wild mushrooms (such as shiitake), chopped into bite-size pieces
1/4 cup sliced green onions
1 teaspoon fresh thyme
5 egg whites
2 tablespoons each chopped fresh herbs (such as chives, parsley, chervil)
Squeeze of lemon

Heat oven to 350 degrees. Heat oil on high in a 6-inch cast-iron skillet for 2 minutes. Add butter; when it foams, add mushrooms. Season with salt and pepper and sauté 5 minutes. Reduce heat to low and add onions and thyme; sauté 2 or 3 minutes. Stir in egg whites with a heatproof rubber spatula until eggs start to set. Transfer skillet to oven and bake 5 minutes, until golden. Sprinkle with remaining herbs and lemon juice. Cut into wedges and serve.