Remove your udon noodles from its package and add it to a pot of boiling water. Stir gently until your udon noodles are separated and pliable. This should take 1 - 2 minutes. They come precooked so avoid overcooking them as they can get too soft.
Rinse and drain your noodles under cold water. If not using right away, drizzle on a little bit of oil to keep them from sticking.
Heat your pan over high heat and add the oil. Add in chicken and stir fry for 4 minutes until browned and cooked through before adding the rest of your vegetables. Stir fry together for 2 to 3 minutes and then add in the noodles and sauce. Continue stir frying for about 3 minutes or until well combined. Serve immediately.
Divide between four serving bowls and garnish with cilantro and green onions.