Slice the pork tenderloin lengthways down the middle, about 3/4 of the way through. Lightly bash with your fist, to flatten a little. Season.
Lay a piece of clingfilm on a work surface followed by layers of Parma ham, slightly overlapping. For a whole tenderloin you will need around 10 slices. Lay the pork onto the Parma ham.
Stuff a layer of Black Pudding down the centre of the pork as well as some hedgerow garlic mustard.
Using the clingfilm, roll the pork over to enclose the filling, then continue to roll and wrap tightly, so that you have a big sausage like shape. Chill in the fridge.
Remove from fridge 15 mins before cooking. For a whole tenderloin, it will take around 25 minutes at 180 degrees. (I used 1/3 for myself and roasted it for 15 minutes).
Rest for at least 5 minutes.
For the quick sauce; add the cider vinegar to a pan on a high heat. Boil until barely anything left. Add the cider, boil until reduce by half then add the Stock & Thyme. Simmer for 5-10 minutes. Add the cornflour at the end for the final 2 minutes to thicken.