Preheat the oven to 200C/400F/Gas 6.
Lightly flour a work surface and roll out the puff pastry to 30x20cm/12x8in.
Remove the skin from the sausages and spread the sausage meat over the pastry, leaving a small border around the edges.
Scatter the fennel seeds over the sausage meat and season generously with salt and freshly ground black pepper.
Brush the edges with a little beaten egg.
With the long end facing you, roll both short sides of the pastry in towards the centre so they meet in the middle, brushing with egg wash as you go.
Cut the roll into 8-10 finger thick slices. Place each one flat on a baking tray.
Brush with a little more egg and then bake for 10-15 minutes, or until golden.
For the sauce, add the chopped apple to a pan with the apple juice and bring to the boil.
When the apples have softened, mash them with a fork or potato masher.
Crack open the cardamom pods and add the seeds to the sauce.
Serve the pastries with the apple sauce.