Preheat oven to 200ºC (390ºF). To make the herb dressing, place the dill, chives, vinegar, sugar, oil, salt and pepper in a bowl and stir to combine. Set aside.
Cut each pastry sheet into 3 strips. Wrap a strip of pastry around each piece of salmon to enclose. Trim the excess pastry with a small knife and place on a lightly greased baking tray. Brush the tops with egg yolk and bake for 12–15 minutes or until puffed and golden. Set aside and keep warm.
Place the beetroot leaves, cucumber and radish in a bowl and toss to combine. Divide between plates and spoon over the herb dressing. Serve with the baked salmon. Serves 12.