Slice the chicken thinly across the grain; this keeps it tender. Clean and slice the mushrooms, mince the garlic, and grate the ginger. Have your noodles measured so they’re ready when the broth is hot.

In a large soup pot or Dutch oven, heat 1 tbsp neutral oil over medium-high heat. Add the sliced chicken, season lightly with salt and pepper, and sear just until it’s mostly cooked through (about 2–3 minutes per side). Remove the chicken to a plate and set aside.

Lower the heat to medium. Add another 1 tbsp neutral oil to the pot. Toss in onion and carrots (if using) and sauté for 3 minutes until softening. Add the mushrooms, a pinch of salt, and cook until they release their liquid and start to brown (~4–5 minutes). Stir in garlic and ginger and cook for 30–60 seconds until fragrant.

Pour in the chicken broth and stir, scraping up any browned bits from the pot. Add soy sauce, rice vinegar (if using), and sesame oil. Bring the mixture to a gentle boil.

Add the seared chicken back into the pot. Reduce heat to a simmer and let everything cook together for 5–7 minutes.

Depending on the noodle type: add egg noodles directly to the pot and cook per package directions (usually 6–8 minutes). If using rice noodles, remove the pot from heat and stir in the rice noodles; let them soften in the hot broth for the time specified on the package (often 4–6 minutes). For udon, follow package timing. Add spinach or bok choy in the last minute.

Stir in green onions and adjust seasoning with salt, pepper, or a splash more soy sauce. If you like heat, add red pepper flakes or a swirl of sriracha. A squeeze of lime just before serving brightens everything.

Ladle into bowls and garnish with extra green onions, a drizzle of sesame oil, and a lime wedge on the side.