• Gather all the ingredients. Bring a large pot of water to a boil for the udon noodles. Once boiling, keep it covered on low heat until you‘re ready to heat the noodles.
  

To Make the Broth from Scratch

• First, make 2½ cups dashi (Japanese soup stock) of your choice. (To make a quick broth with mentsuyu noodle soup base, see the instructions at the end of the recipe.) Here, I‘ll show you how to make a quick dashi using a dashi packet (you can find it on Amazon). In a medium saucepan, add 2½ cups or 600 ml water and 1 dashi packet. Bring it to a boil over medium heat.
  
• Simmer for 2–3 minutes. Then, squeeze the liquid from the dashi packet and discard the packet.
  
• Season the dashi with 1½ Tbsp soy sauce, 1 Tbsp mirin, 1 tsp sugar, and ⅛ tsp Diamond Crystal kosher salt and mix it all together. Cover the pot with a lid to keep it hot and prevent evaporation. Turn off the heat and set aside.
  

To Prepare the Ingredients

• Cut the white part of ½ Tokyo negi (naga negi; long green onion) diagonally into ½-inch (1.3-cm) slices. Set aside.
  
• Thinly slice the leaves and tender stems of 4 sprigs mitsuba (Japanese parsley)(optional).
  
• Cut 1 green onion/scallion into thin slices. Transfer the green onion slices and optional mitsuba to a small plate or bowl for topping the soup later.
  
• Diagonally cut 4 slices narutomaki (fish cakes) (optional). Then, cut 6–8 oz thinly sliced beef (chuck or ribeye) in half to about 1½–2 inches (3.8–5 cm) wide.
  

To Cook the Beef

• Heat the frying pan on medium heat. When it‘s hot, add 1 Tbsp neutral oil and the Tokyo negi.
  
• Sauté the negi until golden brown and tender. Then, add the thinly sliced beef and cook until it‘s no longer pink.
  
• Add 2 tsp sugar and 1 Tbsp soy sauce.
  
• Stir-fry the meat until it is well coated with the seasoning. Remove from the heat.
  

To Boil the Udon Noodles

• Cook 2 servings udon noodles in boiling water according to the package instructions. For frozen udon noodles, boil from frozen for 1 minute to reheat. Drain well and rinse quickly with water to remove the excess starch.
  

To Serve

• Divide the drained udon noodles into individual serving bowls and pour the hot broth to cover.
  
• Place the stir-fried beef, narutomaki, green onions, and mitsuba on top. If you like it spicy, sprinkle shichimi togarashi (Japanese seven spice) on top. Enjoy!
  

To Store

• You can keep the stir-fried beef, udon noodles, and broth separately in airtight containers and store them in the refrigerator for up to 3 days.

To Make the Broth with Mentsuyu (Optional)

• In a medium saucepan, combine ⅓ cup mentsuyu (concentrated noodle soup base), 2⅓ cups water, and 1 Tbsp mirin and mix well. Bring the mixture to a gentle simmer over medium heat. Cover with a lid and turn off the heat. The udon broth is now ready to use.