In small pot, combine water, shiitake mushrooms and kombu. Bring to boil and press down on mushrooms and kombu so they stay submerged. Reduce heat and simmer 20 minutes. Scoop out and discard solids and stir in tamari, mirin and maple syrup. Simmer 5 minutes longer, remove from heat and set aside.
Cook noodles according to directions on package. Drain and set aside. In small skillet, toast sesame seeds until lightly browned and fragrant. Remove from heat, transfer to mortar and add sea salt. Grind with pestle until seeds are half broken and mixture is well blended. Set aside.
Cut stems out of collard greens and stack leaves so they’re all facing the same direction. Roll from one side to the other to form a log and cut crosswise into 1⁄4-inch ribbons.
Heat large cast iron skillet over medium-high heat and add olive oil. Visually divide skillet into five pie slices and place one vegetable in each area—collard greens, onion, carrot, daikon and maitake mushrooms. Sauté 2 minutes pushing ingredients gently with a wooden spoon so that they don’t stick but stay roughly in their defined area. Add water and simmer vegetables until collards are wilted (about 1 minute longer). Push ingredients closer to edge of pan and transfer cooked noodles to center of skillet. Reheat shiitake-kombu stock and pour over noodles and vegetables.
Sprinkle with sesame blend and serve.