The udon soup broth can very easily be made from scratch using three simple ingredients which should be staple items for any Japanese-cooking kitchen: dashi broth, soy sauce, and mirin. Note, the dashi broth can either be homemade or quickly prepared using powder bonito fish (katsuo) dashi.
Depending on the region of Japan, the broth for udon noodle soup varies from dark brown to light brown with varying degrees of saltiness. For this reason, the recipe below can be adjusted by changing the amount of soy sauce that is used. If you are used to a lighter flavor, I recommend starting with two tablespoons of soy sauce, working up to the recommended four tablespoons (or 1/4 cup).
If you’re in a hurry, don’t be ashamed to use a pre-made powder, clearly labeled as "udon soup", which is readily available boxed, at all Japanese grocery stores, and some Asian supermarkets. It can also be purchased online.
If you're pressed for time and don't want to make tempura for this tempura udon dish from scratch, try these shortcuts:
- Use leftover tempura that you made at home the night before. Simply re-heat leftover tempura in a dry non-stick pan over medium-high heat. Do not coat the pan with oil. Turn the tempura over frequently over a 10 to 12 minute period to crisp the tempura. Add this to the bowl of hot udon noodles and broth.
- Use pre-made tempura that can be purchased in the deli section of most Japanese grocery stores, or from your favorite take-out Japanese restaurant.
- Another alternative is to simply use pre-made frozen shrimp tempura that can quickly be fried prior to serving.
- 4-5 pieces vegetables (mixed and shrimp tempura, per person. As a short-cut, leftover tempura or take-out tempura may be substituted for homemade.)
- 1 pkg. Udon noodles (frozen Sanuki style)
- 4 cups water (or substitute with homemade dashi and omit dried bonito dashi powder listed in the ingredients below)
- 1 tablespoon dried bonito (Katsuobushi powder)
- 1/4 soy sauce (shoyu)
- 1/3 cup mirin (sweet cooking sake)
- 1 tsp. sugar (granulated, optional)
- 1 green onion (stalk, sliced for garnish, optional)
- Optional: 3 slices red fish cake (kamaboko, for garnish)
- Optional: Japanese 7-spice chili seasoning (shichimi togarashi, for garnish)
As a short-cut, use leftover tempura or pre-made tempura from a Japanese deli or supermarket. To crisp leftover or pre-made tempura, simply reheat in a dry non-stick pan (do not coat the pan with any oil) over medium-high heat, turning over frequently until crisp.
Set tempura aside.
In a medium pot, bring water to boil and cook frozen udon noodles for 1 to 2 minutes until tender. Drain the noodles well. Separate noodles into two portions and serve in large Japanese-style soup bowls.
Next, make the udon soup. In a separate medium pot, combine water and dried dashi powder mixture (or use homemade dashi using the recipe available here) over medium-high heat. Next, add soy sauce and mirin and bring to a boil. Taste the udon soup. Optionally, a teaspoon of sugar may be added but is not necessary. Adjust the taste of the broth if necessary, by adding more soy sauce if desired. Turn off heat.
Ladle hot broth over the udon noodles, top with crisp tempura. Garnish with green scallions and fish cake. Add Japanese 7-chili spice (shichimi togarashi).