Chop the onion into a fine dice and cut the mushrooms into very small, fine pieces.
Heat 50ml of sunflower oil in a frying pan and add in the chopped onion. Season with half a teaspoon of sea salt and sauté for about 2-3 minutes.
Add the cut mushrooms to the pan. Season them with 1 teaspoon of sea salt and 1 teaspoon of ground pepper. Continue to sauté for 4-5 minutes, stirring frequently.
Transfer it to a bowl and set it aside to cool completely.
Season the pork tenderloin with 1 teaspoon of sea salt, 1 teaspoon of ground pepper, and 2 teaspoon of coriander powder. Massage the seasonings into the meat.
Heat 100ml of sunflower oil then place the seasoned pork tenderloin in the pan. Fry it for a few minutes on each side, turning it until you've created a golden-brown crust all over.
Remove the pork tenderloin from the pan and place it on a plate. Let it cool down completely.
Unroll the puff pastry onto the floured surface. If your tenderloin is particularly long or thick, gently stretch the pastry sheet using a rolling pin.
Arrange the smoked bacon slices neatly in the middle of the puff pastry, laying them side-by-side.
Spread all of the cooled duxelles evenly over the bacon slices then place your seared pork tenderloin right in the middle, on top of the duxelles layer.
Bring one side of the puff pastry over the pork tenderloin, followed by the other, ensuring the meat is completely encased. Seal the ends by folding the excess pastry neatly underneath the roll.
With a knife make a few decorative notches or slits along the top of the pastry. Using a pastry brush, generously coat the entire surface of the roll with the egg wash.
Transfer the roll to a baking dish that's been lined with baking paper. Place the dish into your preheated oven at 180°C Fan (350°F / Gas Mark 4). Bake for approximately 30 minutes, or until the puff pastry is gorgeously golden brown and puffed up.
Video
Notes
Rest the Wellington for 10-15 minutes after it comes out of the oven. This allows the juices to redistribute, ensuring every slice is tender and moist.Ensure both your duxelles and especially your seared pork tenderloin are completely cool before wrapping them in puff pastry. If they're warm, the heat will start to melt the butter in the pastry.When wrapping your Wellington, ensure all seams are tightly sealed. This prevents any juices from escaping and helps the pastry maintain its shape and puff during baking