Udon is one of my all time favorite soups! I love the texture of the  thick noodles and the fact you can customize the toppings you use. This recipe is not a traditional udon soup, but it is super delicious! Although this dish has a number of components, they are all simple and completely worth it. This udon has a beef broth with soy sauce, lime, and a touch of Sriracha to add a great flavor. I top it with tender strips of beef sirloin, sautéed shiitake mushrooms, baby bok choy, cilantro, and scallions. You can experiment with toppings to find your favorite but I have found that this is a perfect blend of flavors and textures.

Ingredients

For the broth:
1 1/2 quarts beef broth
juice of 2 limes
2 tablespoons soy sauce
1 teaspoon sesame oil
1 tablespoon Sriracha (optional)
1 pound udon noodle, cooked according to package instructions

For the beef: 
Peanut oil
1 pound beef sirloin, cut into bite sized strips
1 inch piece fresh ginger, grated
1 teaspoon sugar
2 tablespoons soy sauce
sesame seeds (for garnish)

For the toppings: 
peanut oil
10 ounces shiitake mushrooms, chopped
baby bok choy (see note)
thinly sliced scallions
fresh cilantro
additional Sriracha sauce

Directions

Broth: In a large pot combine all broth ingredients besides noodles. Bring to a boil. Cover and simmer over very low heat until ready to serve.

Noodles: I purchased my udon noodles from an Asian food store and cooked them  without the provided soup base. You can also buy the noodles in the Asian section of some grocery stores. However, these will not be the thick, fresh noodles and they will more resemble spagetti noodles.

Beef: In a medium saucepan heat a drizzle of peanut oil. Add beef, ginger, sugar, and soy sauce. Cook for 7-10 minutes (depending on thickness of strips) or until cooked through. Sprinkle with sesame seeds, remove from pan, and keep warm. Drain liquid.

Mushrooms: In the same pan heat more peanut oil. Add mushrooms and cook over medium heat until soft. Season to taste.

Bok choy: Bok choy comes in varying sizes. I prefer to use baby bok choy for this dish but even so, there is a wide range of sizes baby bok choy come in. If they are larger you can use 4 (1 per person). If they are smaller you can do a few per person.

Bring a small amount of water to boil in a saucepan. Add bok choy, cover, and steam until tender. Very small bok choy take around 3-4 minutes and larger ones can take as long as 10 minutes.

To serve: Spoon udon into the bottom of each bowl. Ladle with broth and top with beef, mushrooms, bok choy, cilantro, and scallions.