For the tart base: Roll out one sheet of puff pastry and cut into a 15cm x 35cm rectangle. Place on a baking tray. Cut 2cm strips from the pastry scraps to trim the edges with. Brush cold water along the border on each edge of the rectangle; set strips on top to frame the edges. Beat 1 egg and brush onto surface of pastry. Chill until firm, about 15 minutes; this is an important step.
Heat oven to 200 C / Gas 6. Bake pastry in preheated oven until it is starting to brown, around 10 minutes. Remove pastry from oven, and reduce heat to 190 C / Gas 5. Press base firmly with back of a fork to collapse it. Return to oven and bake until golden, around 8 minutes. Transfer to rack to cool. This can be made up to 2 days in advance; store at room temperature in an airtight container.
For the white chocolate custard: Heat milk on medium heat in heavy saucepan, stirring, until it comes to the boil. Remove from heat; add vanilla bean to milk, cover, and steep for 10 minutes. Remove vanilla bean. Meanwhile, whip yolks with sugar until thick and light coloured. Whisk in flour and gradually stir hot milk into the yolk mixture, stirring until smooth. Pour into the sauce pan. Bring to the boil over medium heat, whisking constantly, until it thickens. Lower the heat; continue cooking the custard, whisking constantly, until it softens slightly; this should take about 2 minutes. Remove from heat and fold in white chocolate. Transfer custard to a small bowl and cover with cling film. Unwrap when cool and add creme de cacao. This can be made 1 day in advance; cover and refrigerate until needed.
For the Chambord sauce: Puree the defrosted raspberries in a blender and pass liquid through a sieve to remove the seeds; stir in 3 tablespoons Chambord liqueur. Keep refrigerated. This sauce can be made up to 2 days in advance.
When you are ready to assemble the tart, make the glaze. In a saucepan, melt jam over low heat. Remove from heat and stir in 1 tablespoon liqueur. Use while warm.
This tart is best if consumed within 3 to 4 hours of final assembly. Brush bottom of tart with glaze, and sprinkle with half of the almonds. Spoon custard into pastry base and smooth out. Arrange fresh berries over top of custard and brush with glaze. Sprinkle remaining almonds on top. Chill until ready to serve.