prepare the filling , place the black pudding, mince and thyme in a bowl and using your hands mix well into a crumble. Wilt the spinach and remove all excess water using kitchen towel. Pull out a large piece of cling film. Lay the spinach evenly over it to the approximate size of the tenderloin when rolled. Cover the spinach with the black pudding mix evenly. Place the tenderlion on top and use the cling film to help roll in across into a sausage – enclosing the meat mix. Tie into a sausage and chill in the fridge for an hour or freezer for 20 mins.
Roll out the pastry to fit the tenderloin sausage. Unwrapp the pork from the cling film and place on top of the pastry. Wrap the pastry around the pork, use the beaten egg to seal it. Glaze the Wellington with the remaining egg wash. Place in the fridge to chill for a least 30 minutes or leave overnight if cooking the next day.
place in a preheated oven at 200C for 30 minutes until golden brown. To make the sauce add the mustard and sage to the chicken stock, reduced down or thicken with cornflour. Add the cream. Serve the Wellington with the sauce and fresh greens, such as beans or cabbage.