Bring a large pot of water to a rolling boil. Cook the noodles according to the package instructions. Drain, rinse under cold water to stop the cooking, and set aside.
In a medium bowl, combine all of the sauce ingredients.
Whisk until the mixture is silky-smooth, adding a splash more water if needed.
Heat the oil in a large saucepan or wok over medium-high heat. Add the ginger and garlic; sauté for about 2 minutes. Stir in the onion and cook for 1 minute more.
Pour the peanut sauce into the pan and simmer for 1–2 minutes.
Transfer the drained noodles to a large bowl and toss with the warm sauce until every strand is coated.
Toss thoroughly—the noodles should be evenly coated.
Divide among serving bowls and finish with crushed peanuts, sesame seeds, and sliced green onions.