We combine the mustard seeds, cinnamon, pepper, cloves, fennel, and star anise in our mortar and pestle. We smash away for about 5 minutes, grinding up the spices as best we can. We add these to the marinade and stir.
We rinse the pork tenderloin, dry it, and place it on a flexible plastic cutting board. We remove a little fat and some of the tough silverskin. We want the tenderloin to be nicely trimmed. We wash our hands well.
Using tongs, we add the pork to a resealable plastic bag. We cover with the marinade and seal. We place it on a dinner plate on the counter. We could have refrigerated the pork overnight, but we opt to marinate it on the counter for 30 minutes.
Meanwhile, we combine the honey and the rest of the brown sugar in a small bowl. We also pre-heat the oven to 450 degrees.
We remove the pork with tongs to a glass pie pan and pat it dry with paper towels. We pour the marinade into a small pot. We will cook it to be used as a dipping sauce. We spoon about a quarter of the glaze over the top of the pork and place in the oven.
We bring the marinade pot to a boil over medium heat and boil for about 5 minutes. Then we lower the heat and continue cooking while the pork is roasting. When the pork is done, we divide it in small dipping bowls.
Meanwhile, we roast the pork for 5 minutes and then glaze with more of the honey mixture. We continue cooking for another 5 minutes. We turn the tenderloin over with tongs and brush with the rest of the glaze. We return to the oven and cook for another 5-10 minutes. We check with our thermometer and the pork is done after a total of 20 minutes in the oven. We want it to be 160 degrees for our children, but we should have taken it out a few minutes earlier. The pork did not get as browned as we would have liked, next time we may brown it on the stove before roasting it.
We remove the cooked pork from the pan to a clean cutting board with clean tongs. We let rest for 5 minutes and then slice. We serve with the cooked marinade.