Meanwhile, spray a large frying pan with oil spray and cook the bacon and onion if using and set to one side.
In a separate bowl, mix together the yogurt, two of the eggs, mustard powder, 50g of cheese and seasoning.
Now spray a 7" quiche dish with frylight and place 3 bacon rashes on the base. Then add some onions if using, a couple of eggs, yogurt mixture.Repeat and finish with covering all the filling with the remaining yogurt mixture, then the remaining cheese.
Bake in the oven for 20 to 25 minutes until golden.