For the sauce: Combine the sugar, tamari, rice wine vinegar, sesame oil and ginger in a small bowl. Whisk until the sugar is dissolved. Set aside.
For the noodles: Bring a large pot of salted water to a boil. Add the noodles and stir to help submerge them. Cook until the noodles are just barely cooked, 6 to 8 minutes. Drain and rinse with cold water. Using kitchen shears or a clean pair of scissors, cut the noodles into approximately 8-inch lengths. Set aside.
Heat the grapeseed oil in a large skillet over high heat. Add the oyster and shiitake mushrooms and cook, stirring often with a wooden spoon, for about 5 minutes, or until the mushrooms are beginning to brown. Add the shallots and 1/4 teaspoon salt and cook until fragrant, another 2 minutes. Add the red pepper, garlic and scallions to the pan, reduce the heat to medium-high and cook for an additional 3 minutes, or until the peppers are beginning to soften. Add the kale and the cooked noodles and saute another 3 minutes, stirring often to coat the noodles in the oil and to wilt the kale. Add the sauce and toss to coat. Top with sesame seeds if desired.