Using a sharp knife, make an approximately 1/4-inch deep slit down the length of the tenderloin(s), from one end to the other.
In a small bowl, mix the garlic with the sage, salt, pepper and 4 tablespoons of the olive oil. And spread this seasoning paste all over the meat, including inside of the slit.
Tie the meat with kitchen twine, or if you have two smaller pork tenderloin pieces, tie them together one on top of the other. To tie, cut a long string of kitchen twine and wrap it around the meat at one end, about 1-inch from the end. Tie a knot leaving two long ends, and with the remaining string, criss-cross over and around the meat down the length of the meat. Wrap around one more time at the other end and tie another knot. (Though no marinating time is necessary, you may cover and refrigerate for up to 24 hours in advance.)
Heat a large, ovenproof casserole or a deep, 12-inch skillet over medium-high heat. Add the remaining 2 tablespoons of olive oil. Once hot, add the tenderloin and brown on all sides, about 6 minutes total.
If you used a skillet to brown the meat, transfer it to an ovenproof casserole or baking dish. Add 3 cups of water and place in the oven. Roast for 30 minutes, or until the meat is cooked through and the internal temperature reads 150 to 160 degrees Fahrenheit. Remove from the oven.
When cool enough to handle, place the meat on a chopping board and cover with aluminum foil to keep warm. Pour the meat juices into a measuring cup and set aside.
To make the mole verde:
Place the tomatillos, garlic and chiles in a medium saucepan, cover with water and bring to a simmer over medium-high heat. Simmer for 10 to 12 minutes, until the ingredients are completely cooked through and soft, and the color of the tomatillos has changed from light or bright green to olive.
Meanwhile, heat a small skillet over medium-low heat. Add the pumpkin seeds and toast, stirring often, until you hear popping sounds, like popcorn, and they begin to brown lightly, about 3 to 4 minutes. Take care not to burn them. Immediately transfer to a bowl or plate and set aside.
Drain the tomatillos, garlic and chiles and place in a blender (add only one chile at first). Add the salt and puree until smooth. Then add the toasted pumpkin seeds, onion, lettuce, cilantro and parsley to the blender and puree until completely smooth. Taste and blend in the second chile if desired.
Heat the canola or safflower oil in a casserole or heavy soup pot over medium heat. When the oil is hot, add the puree and stir well, being careful as this sauce really likes to jump around; use your lid as a shield. Stir in 1 1/2 cups of the meat juices (or broth or water) and bring to a simmer, cover partially and simmer for 15 to 20 minutes. Stir every 4 to 5 minutes, to prevent the sauce from sticking to the bottom.
If the sauce appears to be cooking too fast and sticking, reduce the heat to low and continue to simmer until very thick. It should coat the back of a wooden spoon heavily. Taste and adjust salt. Turn off heat and keep covered.
To assemble the enchiladas:
Slice and dice, or coarsely chop, the cooked pork tenderloin. If the meat is cold, you may place it back in the casserole after you dice it with any remaining meat juices and heat through over low heat.
Prepare the tortillas for the enchiladas, either heating them on an already heated comal or skillet set over medium heat, or “passing" them through hot oil.
If necessary, reheat the mole verde. One by one, dip a tortilla into the mole verde and place on a plate or chopping board. Place about 1/4 cup of diced meat in the middle and roll into a chubby enchilada. Then place it seam side down on a serving platter. Continue with the rest of the tortillas. Pour the remaining mole verde on top. Garnish with the radish pico and serve.