In a large bowl, put the ingredients for the sauce and mix.
Add the pork and toss to coat well. Reserve in the fridge for 1 hour.
In a saucepan filled with boiling water, cook the udon noodles for 2 minutes. Pour into a colander, rinse thoroughly with cold water to stop cooking and drain. Give one or two chops with scissors to cut the noodles and set aside.
In a very large skillet heated over medium heat, add the oil followed by the onion, carrots, garlic and ginger. Cook 3 to 4 minutes, stirring constantly.
Increase heat to high and add the pork and the sauce. Cook for 2 minutes while stirring.
Add the bell pepper and cook,3 to 4 minutes or until the pork is cooked through.
Add the bok choy and noodles then cook for 3 minutes while stirring.
Remove from the heat, add the bean sprouts and toss. Serve and garnish with green onions!