Pork Tenderloin With Port Sauce

Saw this on Martha, this tastes soooooo good!

• Ready In: 30 mins
• Serves: 4

Ingredients

• 2  tablespoons olive oil or 2  tablespoons  vegetable oil
• 2 (1 lb)  pork tenderloin, silver skin removed, and sliced crosswise into 1 inch pieces
•  coarse salt
•  fresh ground black pepper
• 1⁄2 cup port wine
• 1  cup  chicken stock
• 2  tablespoons unsalted butter
• 1  teaspoon red wine vinegar, plus more to taste if desired

Directions

1. Heat oil in a medium, heavy-bottomed skillet over high heat.
2. Pat pork dry, and season with salt and pepper.
3. Cook pork in oil until brown, about 4 minutes or until cooked to desired doneness.
4. Transfer to a warm platter; set aside.
5. Remove skillet from heat.
6. Discard fat, and add port; return skillet to heat.
7. Deglaze pan, scraping with a wooden spoon to loosen the browned bits from the bottom.
8. Continue cooking until sauce is reduced to about 2 tablespoons.
9. Add stock, and cook until sauce is lightly syrupy, about 4 minutes.
10. Whisk in butter, a little at a time, gently shaking pan while whisking.
11. Stir in vinegar.
12. Taste, and adjust for seasoning.
13. Spoon sauce over pork, and serve immediately.