Preheat oven to 170'C.
Make sure the butter you are using is very cold and has come straight from the fridge. Use very cold water too. Grate or finely dice the butter and then add to the flour and rub with your fingertips until you have fine breadcrumbs. Make a well in the centre and add most of the water and a pinch of salt. Mix the dough without overworking it. You just want to bring the ingredients together. Roll into a ball, flatten slightly and then rest in the fridge.
Roll the pastry out to that it is a little larger than the size of your tart case. Line the case with baking parchment and then lift the pastry into the case and press the edges into the sides. Line with a second sheet of baking parchment and then add the baking beans. Transfer to the oven and blind bake for 15 minutes.
Make the custard: in a bowl whisk together the eggs, egg yolk, milk and cream. Season with salt and pepper.
Peel and thinly slice the onions. Heat a frying pan, add a splash of oil and then the onions. Cook until soft but with a little bite in the centre. Crumble the goat's cheesy by hand. Pick and finely chop the parsley.
Mix the onions, cheese and parsley into the egg mix and season with salt and pepper. Pour into the blind baked tart shell and bake for 40-50 minutes in the oven. The quiche is ready when it is golden brown and has a slight wobble in the centre. Remove from the oven and rest for at least half an hour before cutting.
«Cooking quiches at a lower temperature will give the custard a smoother finish. Lower the temperatures to 130'C and cook for at least an hour and a half.»