First make the filling. Mix together all the filling ingredients with a spatula until well combined. Add salt to taste.
Unroll the pastry but leave it on the plastic sheet it comes on. Place on a baking tray lined with baking parchment. Cut the pastry in half lengthways.
Brush the edge of the pastry furthest away from you with eggwash and arrange half the filling along the length of the pastry. It should be slightly off centre, and slightly closer to you.
Use the plastic sheet to help you roll the pastry over, tucking in with fingers as you go, onto the egg washed edge. Press to seal. Turn the baking sheet around and repeat with the other half of the pastry and filling. Chill in the fridge for 30 minutes.
Preheat the oven to 220 C, 200 Fan, Gas 7. Cut each roll into 4-8 pieces depending on how you plan to serve them- you want larger ones for a picnic, smaller ones for party snacks. Remove the plastic you used to help roll them up.
Arrange on the the baking tray seam side down. Brush with egg wash, then scatter over some caraway seeds and grated cheese, along with a few grinds of pepper.
Bake for 20 minutes, until the filling is piping hot and the pastry golden. Remove from the oven. If the filling is oozing out the ends just tap it back in with a wooden spoon . Cool on a wire rack and serve warm or at room temperature.