Weave the bacon, bake at 350 for 25 minutes, until mostly cooked, but very flexible. The bacon weave needs to be the same length as the loin. If this doesn't work, cut the loin to about 1" shorter than the weave. We will be baking the Wellington for 20-30 minutes, so don't fret about the bacon being raw.
While the bacon weave is baking, rub the salt, pepper, thyme all over the loin, and set aside.
Roll out the puff pastry and trim or re-arrange if necessary (see #2)
Make the mirepoix and set aside.
In a large skillet, preferably cast iron, heat the olive oil on just over medium heat.
Sear the loin for 2 minutes on each side.
Using paper towel, pat dry the bacon weave, and place it on your clean counter.
Preheat the oven to 425.
Spread the mirepoix in an even strip in the middle of the bacon weave.
Place the loin on top of the mirepoix.
Wrap the bacon around the loin.
Place the loin seam-side down in the middle of the pastry.
Fold the top and bottom ends of the puff pastry over the loin, then wrap the sides over the top. Use some egg wash as glue to seal the pastry. ( see #4 )
Place the Wellington seam-side down on a parchment-lined baking sheet.
Brush the top with egg wash, and cut slits in the top to release steam.
Bake for 20-30 minutes, until top is golden brown, and internal temperature is 145F.
Allow to rest for 3 minutes before slicing.