Thaw the puff pastry.
Cut the red cabbage into quarters, remove the stalk and finely shred the cabbage.
Peel, quarter and core the pear and cut into small pieces.
Heat the butter and briefly sweat the onion, garlic, pear and raisins.
Stir in the red cabbage, then the wine and stock and season with salt and pepper.
Simmer for 20-25 minutes, until the liquid has evaporated.
Remove from the heat and leave to cool, then mix in the pine nuts and sage.
Roll out the pastry on a floured work surface to a rectangle measuring 30 x 40 cm.
Put the red cabbage mixture in the middle and spread out on the pastry leaving a narrow border free at the edge.
Roll up from the shorter side.
Place the strudel on a baking tray lined with baking parchment.
Whisk together the milk and egg and brush the pastry with the mixture.
Prick the surface several times.
Bake in a preheated oven (200° conventional oven, 180° fan oven) for about 30 minutes.
Warm the redcurrant jelly slightly, stir in the port wine and use to brush the baked strudel.
Serve garnished with sage leaves.