Preheat oven to 180 degrees C. Fry onion in oil and add mushrooms and fry until all the moisture has evaporated. Using a slotted spoon spoon mixture into 12 muffin pans that have been well sprayed with cooking spray. Divide cheese among the cups and sprinkle over the mushrooms. I
n a mixing bowl combine the eggs, flour and mustard powder. Mix with a balloon whisk until smooth then ad the milk and seasoning.
Pour over mushroom and cheese mixture.
Bake for 20-30 minutes until puffed up and golden brown. Allow to cool slightly in pans then loosen the edges with round bladed knife and serve garnished with chives. Makes 12