• Bring the water to a boil in a pot. Once it boils, turn the heat down to maintain a gentle simmer (boiling makes the stock cloudy). Put the kezurikatsuo into a disposable tea bag, or wrap it in cheese cloth and tie the top.

For the dashi:

• Drop the satchel in the water along with the kombu if you are using it. You can also just put the kezurikatsuo straight into the water and strain it when the stock is done. Let this steep for about 15 minutes, then discard the tea bag, or strain the stock into another pot and discard the solids.

For the Abura-age:

• Add everything except the abura age into a small pot and bring to a boil. Once the sugar has dissolved, add the abura-age and simmer, flip several times until most of the liquid is absorbed and the abura-age is a deep brown color.
• Transfer from the pot to a small bowl and allow it to cool a bit. When it's cool enough to handle, press out some of the excess liquid. You don't want to squeeze all the liquid out, just enough to keep it from being salty.
• Boil a large pot of water and boil the udon for the length of time specified on the package. If the instructions are in Japanese, click here to figure out how long you should boil it for.
• Make sure the noodles are al dente, as they will be sitting in a bowl of hot broth, and you don't want them to go soggy before you're done eating them. When they're done, rinse them under cold water to stop the cooking.
• To finish it all off, put the dashi, soy sauce, mirin and sugar into a pot and heat until it comes to a simmer. Taste it and add salt if you feel like it needs more. Add the noodles to heat through, then divide them into two bowls.
• Top with the seasoned abura-age, scallions and naruto then pour the broth over everything. For a little extra color and kick, you can serve this with shichimi togarashi (Japanese 7 spice chili flakes).