If you don't (or can't) eat spicy food like myself, don't panic yet. This amount of spiciness is "endurable" for people who cannot tolerable spicy food, even me. If you prefer no spicy taste at all for yourself or young children, you can use regular chili bean paste (doubanjiang) and not spicy chili bean paste (la doubanjiang). Of course, if you like it more spicy, please increase the amount based on your personal preference. I hope you enjoy this!
*Note: Powdered dashi packets are available at Japanese markets and are the easiest way to make dashi stock. All you need is boiling water and you'll have dashi stock in a few minutes.
Fill a large pot 2/3 full with water and bring to a boil over high heat. Once it reaches a boil, remove from the heat and set aside until you are ready to cook the noodles.
Heat the sesame oil in a 2-quart pot. Add the garlic and ginger and sauté until fragrant. Then, add the spicy chili bean paste and stir. Add the chicken stock, dashi stock, soy sauce, sake, salt, and sugar and simmer for a few minutes. Check the flavor: It should be a little salty. Strain the soup through cheesecloth into a bowl and transfer back into the pot.
Bring to a simmer and maintain until ready to serve. Loosen up the noodles and place in the boiling water. Cook noodles for slightly less time than recommended by the package directions. (This is because once you pour the soup over the noodles, it continues to cook.)
Drain the noodles completely and transfer to a serving bowl. Pour the soup in the bowl and decorate with the desired toppings. Serve immediately.