Since I didn't have poppy seed in the pantry, I used Nigella seed instead (which has a similar texture), and granulated onion instead of minced dried onion. I also pan-seared the meat first (using the same pan to make the sauce with the drippings), and held it at a slightly longer roasting time at higher temperature of 450F instead of 400F.
2 pork tenderloins
3 tbsp. Honey Dijon mustard (or 2 tbsp. Dijon mustard+1 tbsp. honey)
1 tbsp. granulated garlic
1 tbsp. granulated onion
1 tbsp. nigella or poppy seed
1 tbsp. toasted white sesame seed
1 tsp. kosher salt
4 tbsp. unsalted butter
8 cloves garlic, finely chopped (about 1/4 cup)
1 large shallot, finely chopped (about 1/4 cup)
2 cups low sodium chicken broth
2 cups dry white wine
2 tbsp. sherry or apple cider vinegar
1/2 cup heavy cream
1/2 tsp. black pepper
2 tbsp. finely chopped fresh parsley (preferably Italian or flat-leaf)
1. Place the oven rack in the center of the oven and preheat to 450F.
2. Place a flat rack onto a foil-lined roasting pan or baking sheet and set aside.
3. Add the spice rub ingredients together in a small bowl and mix well to combine.
4. Pat the tenderloins dry with paper towels and place onto a large piece of waxed paper or a platter.
5. Rub the mustard over both tenderloins. Sprinkle the spice rub over the tenderloins to completely cover.
6. Heat 1 tbsp. olive oil in a large skillet and saute the tenderloins, about 2-3 minutes per side, until lightly browned.
7. Transfer the tenderloins to the rack over the baking sheet.
8. Roast the tenderloins for 20-25 minutes or until the internal temperature reaches 140F.
9. In the meantime, make the sauce: using the same pan you browned the pork in, melt the butter over medium-high heat. Add the chopped garlic and shallots and cook 5-6 minutes or until translucent and the butter just starts to brown. Add the chicken stock, wine and vinegar and bring to a boil. Cook for about 10-15 minutes or until the mixture has reduced by half. Add the heavy cream and black pepper and continue cooking over a high simmer, whisking frequently, until the sauce has thickened (5-10 minutes). Turn off heat and stir in the chopped parsley.
10. When the tenderloins have reached an internal temperature of 140F, remove them to a chopping board, loosely tent with foil, and let rest for 8-10 minutes (temperature after resting should be 145F, which is recommended for this cut of pork). Slice the tenderloins, plate, and drizzle with some of the sauce.
11. Serve with the remaining sauce on the side. Great accompaniments for this dish are bulgar wheat with roasted garlic and fresh herbs, and sautéed broccolini.