Preheat the oven to 200°C, 400°F, Gas 6 and put in a baking sheet to warm.
Rub the butter into the flour with the salt until you have coarse breadcrumbs. Add water a little at a time using a round-bladed knife to mix until the mixture just comes together. Form into a ball, cover with clingfilm and refrigerate for 20-30 minutes.
Meanwhile roast the butternut squash or pumpkin in a roasting tin with a little olive oil until completely tender – about 20-30 minutes. When cooked, blend in a food processor or with a hand blender until smooth.
Roll out the pastry and press it gently into a lightly greased flan tin. Prick all over with a fork and bake in the oven on the baking sheet for 20 minutes until pale gold. Whisk together the eggs, egg yolk, cream and crème fraîche then stir in the pumpkin purée and chopped herbs and season. Pour over the pastry base.
Bake in the oven for 35 minutes or until the centre is just set and the filling golden. Leave to cool. Serve.
*This quiche is very rich and indulgent, so shouldn't be eaten too often. But it's perfect for those special occasions.