Wash the turnips and leaves well. Finely slice the handful of turnip leaves. (Place the rest of the leaves aside to use in another dish). Cut the turnips into bite-sized pieces. If they are small, you can simply cut them in half. If they are larger, cut them into quarters or roughly 3/4 inch cubes. Remove the tough stems from the shiitake mushrooms (I put mine in a freezer bag to make stock later). Slice the shiitake tops thinly.
In a skillet, warm 2 Tbsp of the light sesame oil over medium heat. (If using dark, toasted sesame oil, it has a much stronger flavor so use 2 Tbsp butter or olive oil instead of sesame oil for this part of the recipe. Use the dark sesame oil only in the dressing for the noodles). Add the chopped turnips, mushrooms, and salt into the warmed oil and sauté for about 1 minute. Add the 1 1/2 Tbsp maple syrup and 2 Tbsp of water. After about 5 minutes, the water will have evaporated and the turnips and mushrooms will be nicely glazed. At this point, add the sliced turnip greens and cook until wilted and dark green, about 1 more minute. Remove from heat.
While you prepare the glazed turnips and mushrooms, place a large pot filled with 8 cups of water on high heat. Once the water is boiling, add the soba noodles. Cook according to package directions (usually they are done in about 7 minutes). Do not overcook the noodles. As soon as they are done, drain all the water out and rinse the noodles in cold water to remove excess starch (this gives the noodles a lovely texture and ensures they won't clump). If the noodles are too cold after rinsing, quickly dunk them in a fresh pot of boiling water.
In a medium-sized bowl, mix the remaining 2 Tbsp sesame oil, the tamari or shoyu sauce, the rice vinegar, and the fish sauce. Stir well and then add the drained noodles, tossing gently to coat the noodles well.
Serve the noodles with the glazed turnips and mushrooms and garnish with a little cilantro and sesame seeds.