Preheat oven to 220°C bake (or 200° fan bake). Line an oven tray with baking paper.
Unroll pastry onto prepared tray and cut in 6 rectangles. Use a knife to score a 1cm border around the edges of the pastry.
Spread the middle of each pastry with some truffle sauce and then dollop a little onion jam on top. Sprinkle over cheese.
Bake pastry for about 15 minutes, until puffed and golden.
Serve danish warm or at room temperature.