Season the beef fillet with a teaspoon of salt and black pepper. Sear the beef fillet in a pan greased with oil until it is golden brown.
Add chestnut mushrooms and chestnut to the blender with garlic cloves, salt, and black pepper. Blend the mixture nicely.
Cook the ground mixture in a dried pan to release the excess oil.
Then, get ready to assemble. On a cling film, place some slices of Parma ham. Overlap it to add the mixture and wrap the wellington fillet.
Season the ham with a pinch of salt and pepper. Then, spoon out the mushroom mixture and spread it thinly.
Layer the beef on top of the ground mixture and begin to wrap the wellington carefully. Roll out the beef filet nice and tight.
Twist the sides of the cling film and let it sit in the refrigerator to firm up.
Remove the cling film, before yo go ahead to wrap it up with the puff pastry.
Close the edges and roll out tightly with a cling film. Put it back in the fridge again for 5 minutes.
Take out the beef filet rolled with puff pastry. Remove the cling film and brush the egg wash all over the fillet to achieve nice and crispy texture of the beef fillet.
Make slight slit cuts on top to beautify the wellington. Place some dried thyme for enhanced flavors.
Moving forward, place the beef fillet in the oven and bake for 30 minutes at 200 degrees.
Let the wellington rest when it is baked.
Slice the wellington to serve and enjoy!