Do you like pork? Of course you do, that's why we're friends. I'll bet you also like crispy potatoes. I knew it.
Mince up some garlic, and rub it all over your tenderloin, along with salt and pepper. Throw it in the oven until it's done. Meanwhile, cut small potatoes in half, and cook them slowly in a cast iron skillet with olive oil, salt and pepper. Shake and flip for even browning.
When the tenderloin's done (internal temperature of 145 if you listen to the government), remove it to a plate and tent with foil. To the roasting pan, add a cup of stock (I used chicken) with about a teaspoon of cornstarch mixed in. Boil on the stovetop until reduced and nicely thickened. Note: Be careful about adding cold liquid to the hot roasting pan. You might end up with a cracked Le Creuset casserole. Not that I'd know for sure. *cough cough*
Slice the pork, and lay the slices on top of some spinach. Put some potatoes on the plate. Spoon the sauce over everything. Enjoy.