01 - In a small bowl, whisk together the soy sauce, oyster sauce, mirin, sesame oil, and sugar until well combined. Set aside.
02 - Prepare the udon noodles according to package directions. Drain thoroughly and set aside.
03 - Heat 1 tablespoon of vegetable oil in a large skillet or wok over medium-high heat. Add the shrimp in a single layer and stir-fry for 2 to 3 minutes until pink and opaque throughout. Transfer to a plate and set aside.
04 - Add the remaining tablespoon of vegetable oil to the same pan. Sauté the minced garlic and grated ginger for about 30 seconds until fragrant, stirring constantly to prevent burning.
05 - Add the sliced onion, julienned carrot, and sliced bell pepper to the pan. Stir-fry for 3 to 4 minutes until the vegetables are crisp-tender.
06 - Return the cooked shrimp to the pan along with the drained udon noodles. Pour the prepared sauce over everything and toss thoroughly to coat the noodles and ingredients evenly.
07 - Add the baby spinach or bok choy and sliced green onions. Continue stir-frying for 1 to 2 minutes until the greens are just wilted.
08 - Serve immediately while hot, garnished with toasted sesame seeds, shredded nori, and lime wedges alongside.