- Preheat oven to 375 °F.
- Heat oil and butter in large skillet over medium heat.
- Reduce heat to medium-low, and sauté onions until caramelized, about 15 minutes.
- Add Swiss chard, mushrooms, salt and pepper.
- Increase heat to medium, and cook, stirring often, until mushrooms and chard are soft, about 7 minutes.
- Combine apples, flour and nutmeg in mixing bowl, and toss to coat apples.
- Combine eggs, cheese and milk in separate bowl, and beat until ingredients are well blended.
- Fold in apple mixture.
- Spoon chard mixture into pie crust.
- Pour egg-cheese-apple mixture over top.
- Bake 35 to 45 minutes, or until cheese mixture is set and top is browned.
- Cool slightly before slicing, and serve.