Bring a pot of water to a boil and cook the rice noodles according to the package directions (usually 3–6 minutes for vermicelli, a bit longer for wider rice noodles).

Drain and rinse under cold water to stop cooking. Shake off excess water and set aside.

In a medium bowl, whisk together the peanut butter, soy sauce (or tamari), sesame oil, honey or maple syrup, lime juice, minced garlic, and red pepper flakes.

If the mixture is thick, whisk in warm water a tablespoon at a time until a smooth, pourable sauce forms. Taste and adjust salt, sweet, or lime as needed.

Heat a large skillet over low heat. Add the cooked noodles and pour the peanut sauce over them.

Gently toss with tongs or chopsticks until the noodles are evenly coated and warmed through, about 1–2 minutes. If the noodles seem dry, add another tablespoon of warm water.

Transfer to bowls and sprinkle with chopped scallions and crushed peanuts. Add optional protein like sliced grilled chicken, cubed tofu, or sautéed shrimp to make it a full meal.