Cook the Udon Noodles: Bring a large pot of water to a boil. Add udon noodles and cook according to the package instructions (usually about 8-10 minutes). Drain and set aside.
Make the Sauce: In a small bowl, combine soy sauce, rice vinegar, and chili paste. Mix well and set aside.
Sauté the Aromatics: In a large wok or skillet, heat the sesame oil over medium heat. Add minced garlic, grated ginger, and sliced red chilies. Sauté for 1-2 minutes until fragrant, being careful not to burn the garlic.
Add Vegetables: Add snap peas and bell peppers to the skillet. Stir-fry for about 3-4 minutes until the vegetables are slightly tender but still crisp.
Combine Noodles and Sauce: Add the cooked udon noodles to the skillet along with the prepared sauce. Toss everything together gently until the noodles are well coated and heated through, about 2-3 minutes.
Finish with Green Onions: Stir in chopped green onions just before serving for a fresh crunch.
Garnish and Serve: Serve the noodles in bowls, garnished with sesame seeds and fresh cilantro on top.
Notes
Adjust the number of chilies based on your spice preference.