Heat oven to 200C/fan 180C/gas 6.
Heat 75g of the sugar and the vanilla seeds
in a medium, heavy-based frying pan over
a medium-low heat for 5-8 mins, or until
golden brown and caramelised. Add the
apples, currants, sultanas, allspice, nutmeg
and walnuts, then cook for 10 mins or until
the apple is tender. Remove the apple mix
from the pan with a slotted spoon and cool
to room temperature.
Line 2 baking trays with baking paper.
Place a sheet of filo on one of the trays, then
brush lightly with the melted butter. Sprinkle
over 1 tsp sugar. Repeat the process until
there are 3 layers of filo. Repeat with the
remaining sheets of filo on the second tray.
Divide the apple mix along the shorter
edge of both pastry sheets and gently roll
into 2 logs, tucking in the ends as you go.
Brush with melted butter and sprinkle over
1 tbsp sugar. Can be made up to 1 day
ahead, kept chilled. Bake for 25 mins, or
until the pastry is golden brown and crisp.
Let cool slightly, then cut each strudel into
6 diagonal slices. Serve two slices each with
a dollop of crème fraîche on the side.