Preheat the oven to 400ºF and grease a 9x13-inch casserole dish. Set aside.
Massage the pork seasoning into the whole pork loin. Set aside.
Heat olive oil in a large skillet over high heat. When the oil is hot, place the pork loin in the skillet and brown for 3-4 minutes on one side so the pork caramelizes and browns. Remove from the skillet and set aside.
Deglaze the skillet with the white wine and scrape the bottom of the skillet to pull up the brown bits. Add the onion and season with ¼ teaspoon salt. Saute for 2-3 minutes. Add the mushrooms, celery, and carrots and saute again for an additional 4-5 minutes.
Add the garlic and saute until fragrant, about 1 minute. Remove from heat.
Transfer the croutons to the greased casserole dish. Add all of the ingredients from the skillet to the casserole dish and toss until combined. Tuck the herb bundle into the ingredients.
Pour the broth over the casserole and toss until everything is coated in broth. Press all of the ingredients down with a spatula so it absorbs into the bread.
Place the pork loin, browned side up on top of all of the ingredients. Top the bread and pork with the butter.
Cover the dish and bake for 20 minutes. Uncover and bake for an additional 20 minutes.
Remove from the oven when the pork reaches between 140ºF - 145ºF. The pork will continue to cook for 5-10 minutes after you remove it from the oven.
Slice the pork and serve with the toasted bread and vegetables.