In a small frying pan over medium heat, warm the peanut oil. Add the red pepper flakes and cook, stirring, until the oil turns slightly red and the pepper flakes are fragrant. Add the garlic and ginger and cook, stirring until fragrant and slightly soft, about 1 minute Remove from heat. In a small bowl whisk together the sesame oil, soy sauce, balsamic vinegar, and sugar. Whisk in the ginger mixture. Season with salt.
Bring a large pot three-fourths full of water to a boil. Add the salt and the noodles, stir well, and cook until al dente, 2-3 minutes. Drain and rinse under cold running water until cold. Drain thoroughly, then transfer to a large bowl.
Add the sauce and toss to coat noodles. Add the green onions, reserving about 2 tbsp for garnish. Toss to mix. Cover and let stand at room temperature, 1-2 hours, tossing occasionally so the noodles absorb seasonings evenly.
Just before serving, in a small dry frying pan over medium heat, toast the sesame seeds until fragrant and lightly colored, about 5 minute Pour on to a plate to cool. Add seeds and cilantro to noodles. Transfer to a large platter. Garnish with reserved seeds and cilantro and serve.