Rinse the tofu noodles under running water and drain well.
Cut the onion, carrot, bean sprouts, and chives into bite-sized pieces.
Heat cooking oil in a pan.
Stir-fry the onion and carrot, then add the tofu noodles and continue stir-frying.
Add pad thai sauce, bean sprouts, and chives, and stir-fry quickly over high heat.
Mix in an egg.
Garnish with crushed peanuts, lime, cilantro, or other desired toppings to complete.