Soak the rice noodles in warm water as directed on the package, then drain them well.

In a small bowl, whisk together the tamari or soy sauce, maple syrup, fish sauce, rice vinegar, a few grinds of black pepper, and chili flakes until combined.

Heat the sesame oil in a large skillet over medium heat. Add the ground chicken and sliced bell pepper, and cook, breaking up the chicken with a spoon, until the chicken is browned, about 5 minutes. Stir in the butter, shallot, garlic, and a pinch more chili flakes and black pepper; continue cooking until the garlic is fragrant and golden, 1 to 2 minutes.

Add the drained noodles and the prepared sauce to the skillet, tossing everything to coat. Cook for about 1 minute until the noodles are hot and have absorbed some of the sauce. Push the noodle mixture to one side of the skillet, pour the beaten eggs into the empty side, and let them set for about 1 minute. Gently scramble the eggs, then toss them into the noodles. Remove the skillet from the heat.

Add the bean sprouts, most of the cilantro or Thai basil, and most of the green onions; toss everything together.

Serve the chicken pad thai right away, topped with the remaining cilantro or Thai basil, green onions, chopped peanuts, chili flakes, and a squeeze of fresh lime juice.