Soak noodles in boiling hot water for 10-12 minutes until they are tender or cook them according to the package instructions.
Drain the water and toss the noodles with a few drops of oil. Set aside.
In a saucepan, stir together vegetable stock, soy sauce, brown sugar, tamarind paste, chili paste, salt, and water.
Bring the mixture to a boil over high heat. Reduce the heat to low and cook for 3-4 minutes stirring a few times in between. Remove the pan from heat and set it aside.
Heat sesame oil in a wok over high heat. Once the oil is hot, add garlic and red chili and saute for 4-5 seconds.
Add onions, red bell pepper, yellow bell pepper, and bean sprouts, and saute for a minute.
Now add the cooked noodles and the pad thai sauce to the wok and toss well to coat the noodles. Cook for a minute and then switch off the heat.
The noodles will be watery at this stage but they will soak up the sauce in another 3-4 minutes and also become darker in color.
Transfer the noodles to the serving bowls and top with crushed roasted peanuts, cilantro, and lime wedges. Serve hot.