1. Preheat the oven to 350°F.
2. Rub the turkey breast with 1 tbsp olive oil and a good pinch of salt and pepper.
3. Rinse the thyme in hot water to reawaken it, then strip the leaves all over the meat.
4. Place the dried porcini mushrooms in a medium bowl and cover with boiling water to rehydrate.
5. Roughly slice the fresh mushrooms and place them in a safe, stove-top casserole dish with butter and 1 tablespoon of olive oil.
6. Add the porcini mushrooms and some of the water (discard the gritty bit), strip in the rosemary leaves, then add the sundried tomatoes and truffle oil.
7. Cook and stir for 15 minutes, or until lightly golden and the water has evaporated.
8. Pulse in a food processor until fairly fine, season to taste, and leave to cool.
9. To assemble the Wellington, on a clean flour-dusted surface, roll out each pastry block to the size of a shoe box. Then make one 25% larger than the other.

Assembling the Wellington:

10. Lay a sheet of parchment paper on a baking sheet, dust with flour, and lay out the smaller piece of pastry on top.
11. Spread half the mushroom mixture in the middle, roughly the same size and shape as your turkey breast.
12. Place the turkey on top and evenly spread the remaining mushroom mixture on top of it.
13. Lay slices of prosciutto evenly over the turkey breast, overlapping them slightly.
14. Brush the edges of the pastry with a beaten egg. Layer the larger sheet of pastry over the top and gently mold it around the shape of the breast, pushing out air and press to seal.
15. Trim the edges to a width of 1 ½ inches, then crimp the edges by twisting, tucking and pinching the pastry.
16. Brush the whole thing with beaten egg and sprinkle sea salt over the top
17. Cook in the oven for 50 mins to an hour or until puffed up and golden. The internal temperature of the turkey breast should be 160°F. Leave to rest for 10 minutes, then slice into 1-inch thick slices and serve with gravy and cranberry sauce.