Preheat the oven to 180C/fan 160C/gas Lightly grease a 23cm spring form tin.
Roll out the shortcrust pastry to the thickness of a pound coin on a lightly floured surface until slightly larger than the tin.
Line the sides with the pastry trimming any excess. Line the pastry with greaseproof paper and weigh down with ceramic baking beans or any dried pulses you have to hand. Blind bake the case in the oven for 25 mins removing the beans and paper for the last 10 minutes until beginning to crisp.
In a frying pan with a glug of olive fry the onions and bacon together for 8-10 mins over a medium heat until soft and caramelised.
Whisk the eggs and cream together, add two thirds of the cheddar and the softened bacon and onion. Season the mix well with sea salt and black pepper before pouring into the pastry case and topping with the remaining cheddar.
Bake the quiche for 45 minute until golden brown and set, allow to cool before slicing.