Place the olive oil in a large sauce pan over medium heat. Add the onion, garlic, and sage. Cook, stirring frequently, for about 5 minutes until the onions soften slightly.
Add the yams, stir and then add the water. Increase the heat to medium high and when the water begins to boil reduce the heat until it is simmering. Cook, stirring occasionally, for about 20 minutes. As the yams begin to soften use a spoon or spatula to break them up slightly.
Add the parsnips, 1/2 tsp. salt and pepper. Stir and reduce the heat to medium low.
Place a large skillet in the oven and preheat to 425°F.
While the stew is simmering place a sheet of wax paper on the kitchen counter.
Place the pecans in a non-stick skillet over medium-high heat. Cook, stirring frequently, for about 5 minutes. Watch the nuts closely and as they begin to brown reduce the heat to medium.
Add the 1/8 tsp. salt. Cook for about one minute more until the pecans are browned.
Add 2 tsp. maple syrup and let it bubble for about ten seconds shaking the pan vigorously to coat the pecans well.
Remove the pan from the heat and stir the pecans. Turn them out of the pan onto the wax paper to cool. Separate them from each other just after placing on the wax paper so that they won’t stick together.
When the parsnips are just tender, the stew should be thicker and the yams soft. Continue to stir occasionally.
When the oven is hot, spray the pan lightly with oil. Add the pork tenderloin and return the pan to the oven. Cook for about 5 minutes, then turn the pork. Drizzle the remaining 2 tsp. maple syrup over the tenderloin and return the pan to the oven. Cook for about 10 minutes more, turning at least once, until the pork is done.
Remove the pork from the oven and let stand while dishing up the stew into two bowls. Slice the pork and place it on top of the stew and then top with the candied pecans. Serve.