Quick Recipe Version (TL;DR)
Quick Ingredients
- 3 cups (720 ml) low-sodium vegetable broth (or chicken broth)
- 1 1/2 cups (110 g) sliced cremini mushrooms
- 2 tsp grated fresh ginger
- 1 tbsp low-sodium soy sauce
- 2 tbsp white miso paste
- 2 packs fresh udon noodles, 7 oz (200 g) total
- 2 cups (60 g) baby spinach
- 2 scallions, thinly sliced
- 1 tsp toasted sesame oil (optional)
Do This
- 1) In a large microwave-safe bowl, combine broth, mushrooms, ginger, and soy sauce.
- 2) Microwave on High for 4 minutes; stir.
- 3) Add udon (separate strands). Microwave 2 minutes; stir.
- 4) Add spinach. Microwave 1 minute; rest 1 minute.
- 5) Dissolve miso with a few spoonfuls of hot broth, then stir back in (do not boil).
- 6) Taste, add sesame oil if using, and top with scallions.
Why You’ll Love This Recipe
- Fast comfort: A cozy, slurpable bowl in under 20 minutes, using only a microwave.
- Big flavor, minimal effort: Miso, ginger, and soy create a broth that tastes like it simmered much longer.
- Flexible: Easy to swap greens, mushrooms, or add a protein you already have.
- Gentle, balanced heat: Ginger adds warmth and brightness without making the soup spicy.
Grocery List
- Produce: fresh ginger, cremini mushrooms, baby spinach, scallions
- Dairy: none
- Pantry: low-sodium vegetable broth (or chicken broth), low-sodium soy sauce, white miso paste, toasted sesame oil (optional)
Full Ingredients
Soup Base
- 3 cups (720 ml) low-sodium vegetable broth (or low-sodium chicken broth)
- 2 tsp (about 6 g) fresh ginger, finely grated (use a microplane if you have one)
- 1 tbsp (15 ml) low-sodium soy sauce
- 1 tsp (5 ml) toasted sesame oil (optional, for a nutty finish)
Vegetables
- 1 1/2 cups (110 g) cremini mushrooms, thinly sliced
- 2 cups (60 g) baby spinach, loosely packed
- 2 scallions, thinly sliced (greens and whites)
Noodles
- 2 packs fresh udon noodles, 7 oz (200 g) total (vacuum-packed, refrigerated)
Miso (Stir In at the End)
- 2 tbsp (36 g) white miso paste
Optional Toppings (Nice but Not Required)
- 1/2 tsp toasted sesame seeds
- 1/2 tsp chili crisp or chili oil (for heat)
- 1 sheet nori, cut into thin strips
Step-by-Step Instructions
Step 1: Choose the right bowl (and avoid boil-overs)
Grab a large microwave-safe bowl that holds at least 1 1/2 to 2 quarts (1.4 to 1.9 L). Udon soup tends to bubble up as it heats, and a bigger bowl gives you plenty of headroom.
Step 2: Build the broth base in the bowl
In the bowl, whisk together:
3 cups (720 ml) broth, 2 tsp grated ginger, and 1 tbsp soy sauce. Add the 1 1/2 cups sliced mushrooms and stir to coat them in the broth.
Step 3: Microwave to soften the mushrooms
Microwave on High (100% power) for 4 minutes. Carefully remove the bowl (it will be hot) and stir well to redistribute the mushrooms and release their flavor into the broth.
If your microwave is very powerful (1100–1200W), start checking at 3 1/2 minutes. If it’s lower power (700–900W), you may need up to 5 minutes for the mushrooms to soften.
Step 4: Add udon and heat until bouncy and tender
Add the fresh udon noodles to the hot broth. Use chopsticks or a fork to gently loosen and separate the strands (fresh udon can cling together).
Microwave on High for 2 minutes, then stir again. The noodles should be hot and springy. If they are still a bit firm in the center, microwave 30 seconds more.
Step 5: Wilt the spinach without overcooking it
Add the 2 cups baby spinach on top. Microwave on High for 1 minute, then let the bowl stand for 1 minute. The residual heat will finish wilting the spinach gently.
Step 6: Stir in miso the right way (for smooth, savory broth)
Do not boil miso if you can help it; very high heat can dull its flavor.
Scoop out about 1/4 cup (60 ml) of the hot broth into a small bowl or measuring cup. Add the 2 tbsp miso paste and whisk until completely smooth. Pour the miso mixture back into the soup and stir well.
Step 7: Finish and serve
Taste the soup. If you want a deeper aroma, stir in 1 tsp toasted sesame oil (optional). Divide into two bowls if needed, then top with sliced scallions. Add any optional toppings (sesame seeds, chili crisp, or nori) and serve right away while the noodles are at their bounciest.
Pro Tips
- Use a low-sodium broth and soy sauce: Miso adds plenty of saltiness, and it’s easier to season up than to fix an overly salty soup.
- Mix miso with hot broth first: This prevents clumps and helps it blend in silky-smooth.
- Give noodles room: If your bowl feels crowded, split into two microwave-safe bowls before adding udon to avoid boil-overs.
- Slice mushrooms thin: Thin slices cook quickly in the microwave and give you a nicer texture.
- Stand time matters: That 1-minute rest after spinach helps everything settle and finish cooking gently.
Variations
- Protein boost: Add 1 cup (150 g) shredded rotisserie chicken or 7 oz (200 g) silken tofu cubes right after the udon heats through; microwave 30–60 seconds to warm.
- Different greens: Swap spinach for 2 cups chopped bok choy (microwave an extra 30 seconds) or 1 cup frozen edamame (add with mushrooms and increase the first microwave by 1 minute).
- More heat and tang: Stir in 1 tsp rice vinegar and top with 1/2 tsp chili crisp.
Storage & Make-Ahead
This soup is best right after cooking because udon keeps absorbing broth as it sits. If you want to prep ahead, mix the broth + ginger + soy + sliced mushrooms and refrigerate in an airtight container for up to 3 days. When ready to eat, microwave the base, then add udon and spinach as directed.
If you have leftovers, refrigerate for up to 2 days. Reheat gently in the microwave in 45-second bursts, stirring between, just until hot. If the noodles have soaked up too much broth, add 1/2 cup (120 ml) water or broth before reheating. Stir miso in after reheating if possible to keep flavor fresh.
Nutrition (per serving)
Approximate, per serving (1 of 2): 360 calories, 11 g protein, 4 g fat, 68 g carbohydrates, 4 g fiber, 1450 mg sodium.
