I like to make and blind bake the shell in advance. Once you’ve lined the tin with pastry, chill it in the fridge before baking to produce a flakier crust. I blind bake with aluminium foil for good heat distribution and so you get right into the corners, and I like to use sugar because it’s cheap and provides an even weight as the pastry bakes. If there are any cracks in the pastry after blind baking, seal them by brushing a little egg wash over them before filling the quiche. For larger holes or tears, use some excess pastry to fill the gap and brush with egg wash, then return to the oven for a few minutes. Once baked, the shell will keep for up to four days at room temperature in an airtight container.
Store the leftover caramelised onion for 1 week in the fridge. For longer storage, pour into sterilised jars and seal. Store the unopened jars in the pantry for up to 6 months.
Easy to adapt and make gluten-free by using gluten-free flaky pastry.