Start by bringing a pot of water to a boil over high heat. Once boiling, add the chow mein egg noodles and soak them for 30 seconds to 1 minute until they soften. Drain the noodles well using a colander to remove excess water.

In a medium bowl, whisk together the dark soy sauce, regular soy sauce, oyster sauce, fish sauce, granulated sugar, and water until well blended.

Heat 1 tablespoon of corn oil in a large wok over medium heat. Add sliced yellow onions and the white parts of the green onions, sautéing for about 1 minute until softened.

In the same wok, add another tablespoon of corn oil and increase the heat to high. Add the drained chow mein noodles and fry undisturbed for 2 minutes until golden brown and crispy.

Once crispy, reduce heat to medium and add sautéed onions, green onions, bean sprouts, and the prepared sauce to the wok. Toss for about 1-2 minutes until evenly coated.

Remove the wok from heat and drizzle sesame oil over the chow mein, tossing to incorporate the flavor. Serve immediately while hot.