- In a saucepan, bring milk, sugar, vanilla bean and seeds to a boil. Remove from heat, cover and let steep for 10 minutes.
- In a bowl, dissolve cornstarch in cream with a whisk. Add egg yolks and whole egg. Slowly incorporate into infused milk. Cook over low heat, stirring constantly with a wooden spoon or spatula, taking care to scrape the bottom of the pan, until mixture thickens and coats the back of a spoon. Remove from heat and strain. Cover with plastic wrap directly on cream and let cool in the refrigerator or over an ice water bath. Set aside.
- In a food processor, combine flour, sugar and salt. Add butter and pulse a few seconds at a time until it is the size of peas. Add milk and egg yolk and pulse until a ball begins to form. Shape into a disc with your hands.
- On a floured work surface, roll out pastry and line a 20 cm (8 inch) in diameter and 6-cm (2 ½-inch) deep springform pan. Press firmly. Place in the freezer for 15 minutes or 30 minutes in the refrigerator.
- With the rack in the lowest position, preheat the oven to 200 °C (400 °F).
- Pour cooled custard into crust. Cut off excess dough to ½ cm (¼ inch) of the custard level. Place on a baking sheet and bake for about 40 to 45 minutes or until custard is only slightly wobbly. Set the oven to broil and caramelize for about 5 minutes or until surface of custard is partially burnt. Remove from oven. Let cool and refrigerate for 6 hours. Unmould.
Keep flan in the refrigerator, but let it temper before serving.