BBC Food - Recipes - Pork Wellington with black pudding and creamy apple sauce

Ingredients

• 50g/2oz butter
• 3 tbsp vegetable oil
• 1 onion , peeled, very finely chopped
• 175g/6oz chestnut mushrooms , brushed clean, very finely chopped
• 1 garlic clove, peeled, crushed
• salt and freshly ground black pepper
• 1 x 400-500g/14oz-1lb 2oz pork fillet , fat and sinew trimmed
• 1 x 60g/2½oz black pudding round, cut into 1cm/½in strips
• plain flour , for dusting
• 300g/10½oz ready-made puff pastry
• 4 slices prosciutto
• 1 free-range egg , beaten
• 1 Cox or Braeburn apple , core removed, flesh sliced
• 1 tbsp Dijon mustard
• 100ml/3½fl oz chicken stock
• 4 fresh sage leaves
• 50ml/2fl oz dry sherry
• 250ml/9fl oz whipping cream
• steamed green beans
• boiled new potatoes