Grate the cheddar cheese.
Trim, peel and grate the onion.
Finely chop the fresh chives.
Fit the K beater to the machine.
Line the baking tray with parchment paper.
Pre heat the oven to 220ºC.
Add Ingredients 1 (breadcrumbs, cheese, onion, cream, chives, mustard, salt & pepper) into the Mixer bowl.
Attach the Mixer bowl to the machine and fit the splash guard.
Mix on speed 2 for 1 minute .
Add Ingredients 2 (puff pastry) to a lightly floured worksurface.
Using a rolling pin, roll the dough out into a large rectangle about 2 mm thick.
Cut the pastry into equal long rectangles.
Place a line of filling just below the centre of the pastry.
Pull the top edge over the filling to meet the bottom edge and press down.
Use a fork to seal by using the prongs to press down on the edge of the pastry.
Use a knife to divide into individual rolls.
Place individual rolls onto the baking tray.
Brush Ingredients 3 (egg) over the rolls.
Prick each roll on the top 3 times with a fork.
Chill in the fridge for 20 minutes.
Bake for 20 minutes at 220°C.
Serve.