Mix the Marinade ingredients in a bowl.

Place Marinade and pork in a large ziplock bag and marinate in the refrigerator overnight, up to 24 hours.

Remove pork in the marinade from the refrigerator 30 minutes prior to cooking (to bring to room temperature).

Preheat oven to 180C/350F.

Heat olive oil in a skillet over medium high heat. Remove pork from marinade (reserve marinade) and place in pan. Sear until golden brown all over - don't let it burn (Note 2).

Transfer skillet to the oven and roast for 15 to 20 minutes, or until the internal temperature using a meat thermometer reads 145F/62C. (Note 3)

Remove pork from skillet onto a plate and cover loosely with foil to rest while you make the sauce.

Place skillet on the stove over high heat with butter. When the butter is melted, add reserved Marinade and mustard. Whisk until smooth.

Bring to boil, then turn heat down so it is simmering VERY rapidly, and cook until the liquid becomes syrupy - about 4 to 5 minutes. Adjust salt to taste.

Remove skillet from the stove, roll pork in the sauce, then remove and slice. Pour remaining sauce in the skillet into a jug and serve on the side.

I served this with a fennel apple salad on the side. (Note 4)