Place the brown rice noodles in a large bowl of very hot water and soak for 8-10 minutes until they are tender but still have a firm bite, then drain and set aside.
In a small mixing bowl, whisk together the tamari, fresh lime juice, and fish sauce until the flavors are well combined.
Heat the avocado oil in a large wok or non-stick skillet over medium-high heat.
Add the minced garlic and shrimp to the hot pan, sautéing for 2-3 minutes until the shrimp turn pink and opaque.
Push the shrimp to the outer edges of the pan and crack the egg into the center, whisking it quickly with a spatula until it is scrambled and just set.
Add the drained noodles and the prepared sauce to the wok, tossing everything vigorously with tongs to ensure the noodles are evenly coated.
Fold in the bean sprouts, sliced scallions, and red pepper flakes, cooking for only 1 minute more to maintain a fresh, crisp texture.
Transfer the pad thai to a plate and garnish with the crushed peanuts and an extra squeeze of lime before serving.