Preheat the oven to 180C/350F/Gas Mark 4
Roll out the pastry and line a fluted flan dish or 8inch loose bottom cake tin with the pastry.
Line the pastry with parchment paper or (oven safe) cling film and pour in Blind baking beans. Place in the oven and cook for 15-20 minutes until blanched. Remove from the oven, lift the cling film from the pastry and place back in the oven for a further 5 minutes. Remove from the oven and brush some egg wash to seal any gaps. Allow to cool for 2 minutes or until needed.
In the meantime, in a large sauté pan, quickly fry off the onion with the garlic for 2 minutes or until caramelized. Add the spinach and wilt for 30 seconds. Season well with salt and pepper. Remove from the heat and place on the blind baked pastry.
In a separate bowl, beat the eggs, milk and cream together with the seasoning and chopped parsley.
Pour egg mixture over the onion mixture and sprinkle the cheeses.
Transfer to the preheated oven and bake for 25-30 minutes until the eggs are just set.
Remove from the oven and leave to cool for 5 minutes into the tin. Remove from the tin and serve warm or at room temperature.