For pastry, combine flour and butter in a food processor and process until it resembles breadcrumbs. Add enough crème fraiche to bring it together. Tip onto a bench and press mixture together until it just forms a dough. Shape into a disc and wrap in cling film. Refrigerate 10-20 minutes.
For apple filling, place apples and sugar in a medium saucepan with enough water to just about cover them. Add vanilla pod and scraped seeds, bring to the boil, reduce heat and simmer uncovered until apples are tender but still hold their shape. Remove from heat and cool to room temperature.
To form pie, roll pastry between two sheets of baking paper to 3mm thick. Slice pastry into four even pieces and lay one piece into a 10cm pie tin, pressing gently to fit and trimming edges. Repeat with second pie tin. Blind bake for 10 minutes or until just cooked. Sprinkle a spoonful of almonds over each base and cover with apple filling. Cover each pie with another piece of pastry to make the lid, press down firmly on the edges to seal and trim neatly. Brush lids with egg wash and sprinkle with sugar. Bake for 20-30 minutes until golden and pastry is cooked.
For vanilla custard, whisk egg yolks and sugar together. Heat milk and cream in a small saucepan with vanilla seeds and scraped pod until just below boiling. Pour slowly into egg yolk mixture, stirring continuously. Strain mixture into a clean saucepan and cook gently, stirring, until custard coats the back of a spoon.
Serve pie warm or cold with custard on the side and cream if desired.