Heat the oven to 400º F.Remove any silverskin from the tenderloin. Season on all sides with salt and pepper.
Heat an ovenproof skillet on the stovetop; when hot add the olive oil. Add the tenderloin and sear on all sides until well browned, about 10 minutes. Place the pan into the oven to cook about 20 minutes more or until 145 degrees F. (Just pink)
Meanwhile, in a bowl or mixing cup, combine the wine, broth, mustards, and cornstarch. Mix well. Set -aside.
Remove the pork from the oven and move to a cutting board. Cover lightly with foil and allow to rest for at least 5 minutes.
When the pork is resting, put the skillet back onto the stove-top; give the cornstarch mixture a nice stir then pour into the skillet, use a spoon to loosen any browned bits from the bottom of the pan, stir until the sauce has thickened. Turn off the heat and swirl in the butter, if using. Taste and season with salt and pepper.
Slice the tenderloin into ½ inch slices, arrange on a warmed plate and spoon the sauce over. (In my case, I started with a spoonful of my veggies, braised leeks, and peas, then placed my first couple of pieces of tenderloin on that, then spooned the sauce over...)