Ingredients for 4 servings:
1. 2 tablespoons balsamic vinegar
2. 1 tablespoon olive oil
3. 1 tablespoon fresh thyme
4. 2 teaspoons Dijon mustard
5. 1/2 teaspoon ground black pepper
6. 1 lb pork tenderloin, trimmed of all visible fat
7. 2 shallots, minced
8. 2 (5 ounce) bags baby spinach leaves
9. 1/4 teaspoon salt

Directions:
1. Combine the vinegar, 2 teaspoons of oil, thyme, mustard, garlic and pepper in a large ziplock bag. Add the pork. Squeeze out air and seal the bag, turn to coat the pork.
2. Refrigerate at least 4 hours up to 24 hours.
3. Preheat the oven to 475.
4. Spray a small roasting pan with nonstick spray.
5. Remove the tenderloin from the marinade, discard the marinade.
6. Spray a skillet with non stick spray and set over medium high heat. Add the pork and cook, turning occasionally, until browned, about 5 minutes. Transfer to a roasting pan.
7. Roast until and instant read thermometer inserted into the thickest part of the pork reads 160, about 20-25 minutes.
8. Transfer to a carving board, let stand 10 minutes.
9. Meanwhile, heat the remaining 1 teaspoon of oil in a nonstick skillet over medium high heat. Add the shallots and cook until softened, about 2 minutes. Add spinach and salt, cook about 3-4 minutes. Serve with pork.