Heat a medium pot over medium heat and add vegetable oil. When shimmering, add the sliced onion and sauté 6–8 minutes until soft and beginning to caramelize. Add minced garlic and ginger and sauté 30–45 seconds until fragrant.

Add vegetables and stock

Add the carrot and potato cubes to the pot and stir to coat. Pour in the dashi stock and 1 cup water. Increase heat to bring to a gentle boil, then reduce to a simmer. Skim any foam, cover partially, and simmer 10–12 minutes until potatoes and carrots are tender when pierced with a fork.

Finish curry base

Lower heat to low. Break the Japanese curry roux into pieces (if using blocks) and whisk into the warm broth until fully dissolved. If using powdered/ homemade roux, whisk until smooth. Stir in soy sauce, mirin, salt, and black pepper. Simmer on low 3–5 minutes to thicken and meld flavors. Taste and adjust seasoning (more soy for saltiness, a pinch of sugar if overly bitter). Keep warm on the lowest heat while preparing noodles and protein.

Protein (Optional)

If using protein, combine the thinly sliced beef or chicken with 1 tsp soy sauce and dust lightly with 1 tsp cornstarch. Heat a skillet over medium-high heat with a small drizzle of oil. When hot, add the meat in a single layer and sear quickly, 1–2 minutes per side for thin beef, 2–3 minutes for chicken, until just cooked through. Remove and set aside on a plate. Any browned bits can be gently deglazed with a tablespoon of the hot curry broth and added back to the pot for flavor.

Noodles & Garnish

Cook udon noodles according to package instructions (fresh/frozen: 2–3 minutes in boiling water; dried: 8–10 minutes), stirring occasionally to prevent sticking. Drain and rinse briefly under warm water to remove surface starch and keep noodles pliable.

Divide cooked udon evenly among 4 bowls (servings). Ladle the hot curry broth over the noodles, ensuring a good balance of vegetables and broth. Top each bowl with the cooked protein (if using), then sprinkle sliced green onions. Finish with 1/8 tsp toasted sesame oil and a pinch of shichimi togarashi per bowl if desired. Serve with pickled red ginger or fukujinzuke on the side.