Preheat the oven to 200˚C.
Line the puff pastry on a work surface and roll into a square either 4 individual 10X10cm squares or a larger to share 20X30cm square. Place on a baking tray set with parchment paper.
Brush the edges of the pastry with egg wash.
Next, scatter the slices of potatoes, nduja sausage and onion.
Place the taleggio cheese and sprinkle the parmesan.
Place in the oven and bake for 15-25 minutes until well coloured and bubbling.
Remove from the oven, portion into 4 pieces, and serve immediately with some rocket leaves.