Looking for a noodle soup that will warm you up in more ways than one? Look no further! This fantastic udon soup recipe features homemade stock, delectable roast pork belly, spicy gochujang paste, and crisp-tender leaves of bok choy.Jump to Recipe Print Recipe
What is Udon?
Udon are thick, wheat-based Japanese noodles. They have a little chew to them, and are quite delicious. Many US brick and mortar and online markets carry a dried variety (that’s what I used the day I photographed this recipe), but I actually prefer the thicker frozen ones that my local Asian grocery keeps in stock. Either is fine for this recipe.
I Don’t Have any Udon Noodles – Can I Still Make This?
Yes, absolutely! This soup would be great with ramen noodles (leave out the seasoning packet), and you could even use spaghetti or linguine in a pinch. Any long noodle that holds up to sitting in broth would work just fine, so if you have dietary restrictions you can use any noodle that fits that description.
Ingredients for Spicy Udon Noodle Soup
Udon Soup Broth
For this spicy udon soup recipe, I used my Easy Broth for Ramen or Udon Soup. If you have little more time and energy on your hand, you could also make the Momofuku-style Ramen Broth from my site. Both are Instant Pot recipes and can be easily made ahead and refrigerated or frozen. If you’d like to go the easy route, you could use chicken or pork stock, or this ramen broth in a box (my local supermarket carries it, as does amazon). Whichever broth you use, the spice comes from gochujang paste – see below
Gochujang paste is a spicy Korean fermented soybean paste. I think of it as a spicy miso, and I love it. I’d put it on everything if my kids would learn to like spicy food. It’s becoming popular enough that my big box supermarket carries it, but you can also pick it up on amazon or from an Asian grocery. If you can’t find it, you can substitute sriracha or chile garlic paste to taste.
I add gochujang at the end of cooking, right before serving the soup. It’s a thick paste, and the best way to incorporate it is to thin it out with about a half cup of broth in a separate bowl before adding it to the soup. Add half of the thinned out gochujang first, mix it well, and taste the soup – then decide if you’d like to add the rest!
What if We Don’t All Like Spicy Food?
If you don’t like heat, leave the gochujang out! I love spice, my husband likes it, and my kids have been known to complain about black pepper (although the 8 year old is getting better). When I serve this to them, I make the soup as directed up to right before the gochujang is added, but fill two bowls before I mix it in. I serve my kids, then add the heat, then serve my husband and myself. Then I put extra sriracha or chile garlic on the table for myself.
Roast Pork Belly
There just isn’t a great short cut to delicious pork belly, unfortunately. I start by coating the slab with a salt and sugar rub, tightly wrapping it in plastic, and refrigerating it over night. It’s not remotely labor intensive, but you do have to plan ahead. Preferably it would sit in the sugar/salt mixture for 12-24 hours, but a little longer won’t hurt.
After that, it has to be roasted. This can all be done in advance on the weekend if you like. It’s also super easy, but again takes time. Roast it in a 450 oven for 1 hour (for a 2 -3 pound slab of belly), then reduce the heat to 250 and roast for another 30 minutes. It can be refrigerated again at this point until ready to use.
Before assembling the soup, slice the pork belly into 1/2 inch thick slices, and pan-fry them for about 3 minutes per slide. The goal isn’t to make them crispy like bacon. You’re just heating them up and adding color.
That Sounds Like a Lot of Work
It’s not a lot of work for me, because I cure my own bacon. I always cut off a slab of pork belly to use immediately the day I put the rest in the cure, so I give it a quick salt and sugar rub and pop it in the fridge. I cut a 2-3 pound slab, even though I’m not going to use it all in for udon soup. I roast the pork belly on Saturday or Sunday, and we get 2-3 dinners out of it during the week.
Other Ways to Use Roast Pork Belly
- Pork Belly Ramen
- Pork Belly Bao Buns with hoisin and quick pickles – you can buy the buns at an Asian grocery
- Pork Belly Lettuce Wraps (Bossam)
- Pork Belly Rice Bowls (Bibimbap – you can use meat and toppings of your choice!)
Where Can I Buy Pork Belly?
Pork belly is tough to find at mainstream big box supermarkets where I live. My Costco carries it, and it’s honestly the only reason I rejoined. Some Sam’s Clubs do as well, but ours doesn’t (call ahead). Asian and Latinx groceries are your best bet, or a real butcher shop.
Substitutes for Roast Pork Belly
If you don’t want to roast pork belly, or can’t find it locally, you can still enjoy delicious spicy udon soup. You can leave it out entirely, and enjoy the other ingredients alone, or you substitute another type of meat. I encourage you to try to get your hands on some though, it’s worth the trouble!
Pulled pork shoulder would be fantastic in this soup if you have some leftover. You could also grill or roast a pork tenderloin – they only take 20-30 minutes in the oven. Slice it thin and add it to the soup. Leftover (or rotisserie) chicken or duck would be good too! Obviously changing the meat will change the recipe pretty significantly, but should still make a delicious soup.
Bok choy is a Chinese cabbage that stands up well to stir fries and braises. Cut off the white heel end, wash the leaves well, and roughly chop. Add to the soup. If you can’t find bok choy, you could substitute another green such as Napa cabbage, Swiss chard, or kale.
To prepare shiitakes, chop off the tough stem and either discard or save to flavor stocks. Slice thinly. Add to the soup.
There are many different types of tofu out there, with varying amounts of moisture. Avoid silken – it will fall apart in soup. Regular tofu is sold as medium, firm, extra firm, and super firm. I recommend firm or extra firm, although the other two will work as well.
Tofu comes packed in water, which should be discarded. The tofu block should then be sandwiched between a layer of paper towels, and a heavy pan placed on top. Press it for 10-20 minutes, then cube and add to the soup.
Ramen and udon noodle soups are fantastic with a halved hard or soft boiled egg on top. I like both equally, so make whichever your family prefers. If you have some extra time, you can also make a batch of ramen eggs, but it isn’t necessary.
Chop a few scallions and add a sprinkle to each bowl just before serving. Chives would also work well.
What to Serve With Spicy Udon Soup
This is a hearty soup, packed with noodles, veggies, and 3 kinds of protein. You really don’t need anything else with it. If you want a little variety though, I’d stay in the region:
- Gyoza – make my Bacon and Shrimp Gyoza recipe, or use your favorite frozen brand
- Egg Rolls
- Spring Rolls
- Seaweed Salad
- Korean Green Salad
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Spicy Udon Soup with Pork Belly and Bok Choy
Roast Pork Belly
- 2-3 lb pork belly 1 lb needed for recipe
- 1/4 cup salt
- 1/4 cup sugar
Spicy Udon Soup
- 12 cups udon broth (may substitute storebought ramen, chicken, or pork stock)
- 12 oz bok choy cleaned and chopped
- 4 oz shiitake mushrooms cleaned, stems removed, sliced1.
- 14 oz extra-firm tofu pressed, cut into 1/2" cubes
- 1 lb roast pork belly
- 6 eggs soft or hard boiled, halved
- 1/4 cup soy sauce
- 1/4 cup gochujang paste
- 1/2 cup scallions diced
- udon noodles (1 package of frozen noodles or 1 bundle of dried per person)
Roast Pork Belly
- Mix together sugar and salt. Rub all over pork belly. Wrap in plastic wrap and refrigerate 12-24 hours.
- Preheat oven to 450F. Roast pork belly for 60 minutes, basting halfway through, and covering with foil if it turns dark brown. Turn heat down to 250 and roast an additional 30 minutes. Remove from the oven and either refrigerate for up to 3 days or immediately proceed with the recipe. Only 1 pound is needed for the soup, so reserve the rest for another purpose.
Spicy Udon Soup
- Put a pot of water on to boil, and cook udon noodles according to package directions.
- Heat stock in a large pot over medium heat until simmering. Add bok choy, shiitakes, and soy sauce. Cook 7 minutes.
- Add cubed tofu. Cook 5 minutes.
- Cut pork belly into 1/2 inch slices, and fry each over medium heat for 3 minutes per side.
- Ladle 1/2 cup hot broth into a bowl. Add gochujang paste. Stir/whisk until well-combined. Add half of this mixture back into the soup and check the spice level of the soup broth. If you'd like more spice, add the rest.
- Assemble the soup: ladle soup over noodles in each bowl, and top with pork belly slices, halved hard or soft boiled eggs, and scallions. Enjoy immediately.