Chuck your chopped shallot and apple into a pan on a medium heat with a splash of olive oil and cook gently until softened, remove from the heat and while still warm add your chopped sage and leave to cool
In a bowl add your pork mince, black pudding, cooked shallot mixture, breadcrumbs and half your egg yolks and mix well until all fully incorporated and season with sea salt and black pepper
Dust your surface with flour and roll out your puff pastry, and cut into two pieces, arrange your pork mixture into a sausage shape down the length of each pastry rectangle, Brush the surrounding pastry with some beaten egg. Bring one long edge of pastry over the meat and press down against the bottom length of pastry to seal it. Press along the whole length to seal
Score the pastry along the top of your sausage rolls at 1cm intervals and brush with the remaining egg yolks
Slice each roll into six even pieces and place on a baking sheet. Bake for 20 to 30 minutes or until golden brown and cooked through.