Preheat your oven to 190°C/gas mark 5.
Firstly in a large bowl mix the pork mince, black pudding, parsley, sage, mace, cayenne pepper and mustard with a good pinch of salt and black pepper. Then mix well and squidge together.
Roll the block of pastry out into a large rectangle 40 x 30cm. Put the filling down the middle in a neat sausage shape, and square off the edges of the pastry.
Roll the pastry over the meat then pull the other side of the pastry up on top.
Square off the ends then turn the roll over so the fold is underneath.
Divide into six, then slash each sausage roll a few times and brush with beaten egg.
Finally, bake in the oven for 30 minutes until golden brown.