Add flour to bowl along with butter and "rub in" using your finger tips to achieve crumb like texture. Add egg yolks and mix through with wooden spoon. Add water very gradually, whilst gathering the pastry to form a ball. (only add enough water to bring the pastry together). Wrap the pastry in cling film and chill for 20 mins. Meanwhile prepare the filling by mixing the cream and crème fraiche together followed by the eggs and egg yolks with a balloon whisk. Preheat oven to 180°C, 350°F, Gas Mark 4. Remove pastry from fridge and roll out on floured surface. Line pastry tin. Place back in fridge for 15 mins. (don't be tempted to skip this stage as I have done in the past as your pastry will shrink). Remove lined tin from fridge and brush pastry lightly with egg white. Place in oven for a couple of minutes. Remove from oven and scatter cooked bacon pieces on the pastry base. Then add grated cheese followed by cream mixture. Place on middle shelf of oven and cook for 30-40 mins until mixture has risen and is golden on top. Allow to stand for 5-10 mins before seving. Serve hot or cold. Gaynor's Tip: If using for a picnic it is best transported whole and covered in the tin.