Vegetarian Curry Udon with a Savory Broth

Vegetarian curry udon is a Japanese-style noodle dish of thick udon served in a savory curry broth with vegetables. This version builds flavor with kombu, mushrooms and a simple curry-flour thickener, so the sauce clings to the noodles without needing meat or a packaged curry roux.

Ingredients

4 portions frozen udon noodles, about 28 oz (800 g) total
5 cups (1.2 L) low-sodium vegetable broth
1 piece dried kombu, about 4 by 4 inches (10 by 10 cm, roughly 5 g)
1 tablespoon (15 ml) neutral oil, such as canola or sunflower oil
1 medium yellow onion, about 5 oz (150 g), thinly sliced
1 medium carrot, about 3½ oz (100 g), peeled and cut into thin half-moons
8 oz (225 g) cremini or shiitake mushrooms, sliced
2 garlic cloves (about 6 g), finely chopped
1 tablespoon (10 g) finely grated fresh ginger
2 tablespoons (16 g) all-purpose flour
2 tablespoons (12 g) Japanese curry powder, mild or medium
2 tablespoons (30 ml) soy sauce
1 tablespoon (15 ml) mirin
1 teaspoon (4 g) sugar
½ teaspoon (3 g) fine salt, plus more to taste
2 scallions (about 30 g), thinly sliced, for serving
1 teaspoon (3 g) toasted sesame seeds, optional
1 teaspoon (5 g) chili crisp or chili oil, optional, for serving

Instructions

Prepare the ingredients. Slice the onion, carrot and mushrooms, then chop the garlic, grate the ginger and slice the scallions. Measure the flour, curry powder and seasonings before you begin cooking; once the broth is hot, the thickener needs steady stirring to stay smooth. If your frozen udon portions are stuck together, leave them frozen until you are ready to cook them.
Make a quick kombu broth. Add the vegetable broth and kombu to a large saucepan or Dutch oven. Bring it slowly to a gentle simmer over medium heat, then simmer for 10 minutes. Avoid a hard boil, which can make kombu broth taste harsh or slippery. Lift out and discard the kombu with tongs. Keep the broth warm nearby while you cook the vegetables.
Soften the vegetables. Heat the oil in the same pot over medium heat. Add the onion and carrot and cook for 4 minutes, stirring now and then, until the onion begins to turn translucent. Add the mushrooms and cook for another 2 minutes, allowing their moisture to cook off. Stir in the garlic and ginger and cook for 1 minute, just until fragrant; browned garlic can taste bitter.
Make the curry base. Sprinkle the flour and curry powder over the vegetables. Stir continuously for 1 minute so the flour is distributed and loses its raw taste. Pour in about 1 cup (240 ml) of the warm broth a little at a time, whisking or stirring firmly after each addition to loosen any floury bits. Once smooth, gradually stir in the remaining broth.
Season and simmer. Stir in the soy sauce, mirin, sugar and salt. Bring the pot to a gentle simmer and cook for 5 minutes, stirring occasionally, until the broth thickens enough to lightly coat a spoon and the carrot is tender but not mushy. Taste a spoonful and adjust with a little more soy sauce for savoriness, salt for overall seasoning, or a splash of broth if it has become thicker than you like.
Cook the udon and serve. While the broth simmers, cook the frozen udon in a separate pot of boiling water according to the package directions, usually 1 to 3 minutes, separating the strands gently with chopsticks or tongs. Drain well; a quick rinse under warm water can remove excess surface starch if the noodles seem sticky. Divide the noodles among four bowls, ladle the hot curry broth and vegetables over them, and finish with scallions, sesame seeds and chili crisp if using. Serve right away while the noodles are springy.

Tips

Choose a low-sodium broth. Soy sauce and curry powder blends can vary in saltiness, so starting with low-sodium vegetable broth gives you room to adjust at the end. If your broth is already salty, leave out the measured salt until you taste the finished curry.
Keep the thickener lump-free. Coat the vegetables well with the flour and curry powder, then add warm broth gradually while stirring. Adding all the cold broth at once can leave small flour lumps that are difficult to whisk out later.
Use a practical kombu substitute if needed. Kombu is dried kelp and gives the broth gentle, sea-like umami. If you cannot find it, omit it and stir 1 teaspoon (5 g) white miso into the finished broth off the heat, or use an extra teaspoon of soy sauce; either option gives a slightly different, less clean kelp flavor. Do not boil miso hard, because its aroma is best preserved at the end.
Adjust the curry to your powder. Japanese curry powder is usually rounded and aromatic, but blends differ. Start with 1½ tablespoons if yours is hot or very pungent, then add more after simmering. The broth tastes a little less intense once it is mixed with a full portion of noodles.

Serving Suggestions

Serve curry udon as a complete, filling bowl with a small side dish rather than adding too many toppings to the broth. Steamed greens, blanched spinach dressed with sesame, or a crisp cucumber salad offer freshness and a contrasting texture. A simple bowl of rice is also useful for soaking up any curry broth left at the bottom, though the udon itself is substantial.

Set scallions, sesame seeds and chili crisp on the table so each person can finish their own portion. A little chili oil adds heat and aroma, while toasted sesame adds a nutty note; both are optional because the curry broth is already well seasoned. If serving several bowls, warm them with hot tap water and dry them before filling so the noodles stay hot longer. Keep the broth just at a gentle simmer until the noodles are ready, but do not leave cooked udon sitting in it for long or it will continue absorbing liquid.

Variations

Add tofu: For more protein and a different texture, add 8 oz (225 g) firm tofu, cut into ¾-inch (2 cm) cubes. Pat it dry and brown it in the pot with a little extra oil before cooking the onion, then set it aside and return it to the broth for the last few minutes. This keeps the tofu from breaking apart as you stir the curry.

Change the vegetables: Thinly sliced cabbage, zucchini, green beans or small broccoli florets work well. Add sturdy vegetables such as cabbage and broccoli with the carrot; add quick-cooking zucchini or green beans during the last 3 to 4 minutes of simmering. Keep the total amount close to the recipe’s roughly 4 cups (about 500 g) of sliced vegetables so the broth remains plentiful.

Make it vegan or gluten-free: The listed ingredients are vegetarian, and they can be vegan if the curry powder and noodles contain no animal-derived ingredients; check package labels, especially for udon that may contain egg. For gluten-free bowls, use certified gluten-free noodles, tamari instead of soy sauce, and a gluten-free all-purpose flour blend. The texture of the broth can vary with different flour blends, so add the broth gradually and simmer until it reaches the consistency you prefer.

Make it richer or hotter: For a rounder broth, stir in ¼ cup (60 ml) unsweetened coconut milk at the end; it softens the curry’s spice and gives the soup a creamier finish. For more heat without changing the whole pot, add chili oil to individual bowls. You can also add ½ teaspoon (2 g) freshly ground black pepper to the curry base for warmth that is more peppery than fiery.

Storage and Reheating

For the best texture, store the curry broth and cooked udon separately. Let them cool briefly, then refrigerate within 2 hours in airtight containers. The broth with vegetables keeps for 3 to 4 days in the refrigerator; cooked noodles also keep for 3 to 4 days, although they soften and stick together as they sit. If they are already combined, the dish is still best within 1 to 2 days because the noodles absorb broth and become less springy.

Reheat the broth in a saucepan over medium heat, stirring occasionally, until steaming throughout. Add a splash of water or vegetable broth if it has thickened in the refrigerator. Reheat leftover food to 165°F (74°C); use a food thermometer to check the center of a substantial portion. Warm the noodles separately in boiling water for about 30 seconds, drain, and put them into bowls before adding the hot broth. Avoid freezing assembled bowls, since udon can turn soft after thawing. The broth alone can be frozen in a sealed freezer-safe container for up to 2 months, with some loss of fresh vegetable texture.

Frequently Asked Questions

Is curry udon vegetarian?

It can be, but some curry udon uses dashi made with bonito flakes or a curry roux containing animal ingredients. This recipe uses vegetable broth and kombu, a dried kelp, for a meat-free savory base. Check the labels on your udon, curry powder and any optional toppings if you are cooking for someone who avoids all animal products.

Can I use shelf-stable or fresh udon instead of frozen?

Yes. Follow the package directions, since shelf-stable, refrigerated and frozen noodles need different cooking times. Cook the noodles separately from the curry broth and drain them before serving; this prevents excess starch from clouding the broth and makes it easier to control how soft the udon becomes.

How can I make the curry broth thicker?

Let it simmer for another 2 to 3 minutes, stirring often, so some liquid evaporates. If you want a much thicker broth, mix 1 teaspoon (3 g) flour with 1 tablespoon (15 ml) cool water until smooth, stir it into the simmering pot, and cook for at least 2 minutes. Add thickener sparingly: the noodles will absorb broth as the bowl stands.

What can I use instead of mirin?

Mix 2 teaspoons (10 ml) water with 1 teaspoon (4 g) sugar and use that in place of the tablespoon of mirin. Mirin contributes mild sweetness and a rounded flavor, so the simple substitute will taste a little less complex. Taste the broth before adding more sugar, particularly if your vegetable broth is already sweet.

Can I make the broth ahead?

Yes. Prepare the curry broth and vegetables up to 3 days ahead, cool and refrigerate them promptly, then reheat them gently while you cook fresh udon. The broth may thicken as it chills; loosen it with a little water or vegetable broth. Cooking the noodles just before serving gives the dish a noticeably better texture than storing them in the broth.

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