1. To make the mushroom duxelle: in a food processor, using the pulse function, blitz the mushrooms until they are the size of a grain of rice, then place them into a bowl. 
2. Heat the olive oil in a frying pan, add the mushrooms, along with the rosemary and the sherry wine. Cook, stirring occasionally, until the wine has evaporated and the mixture has softened (10min approx). Add the butter and stir until fully melted and integrated. Reserve and leave the duxelle to cool.
3. Season the Presa and sear in a hot frying pan or on a griddle.  Leave to cool.
4. When all the ingredients are at room temperature, lay the slices of ham in a sheet of cling film. Add a layer of the duxelle and then place the Presa on top.  Wrap the Presa tightly with the help of the cling film. Let it rest in the fridge for at least a couple of hours.
5. Prepare a couple of pancakes following your favourite recipe and wrap the meat with it (having removed the cling film). 
6. Preheat the oven to 200°C, 180°C fan, gas mark 6.  Unroll the pastry onto a baking sheet.  Trim a 2cm strip off one long side and reserve.
7. Place the pancake-wrapped presa in the centre. Brush the edges of the pastry with beaten egg, then fold the pastry to completely encase the Presa. 
8. Use the reserved pastry to cut shapes to decorate the Wellington, then brush with the remaining egg.
9. Bake for 25/30 minutes.
10. Leave to rest for at least 5 minutes before slicing to serve.

Little tip:

This recipe lends itself to advance preparation, perfect when entertaining. The whole Wellington can be made the day before, ready to bake for minimum stress!