1. Bring a large pot of water to a boil and add in udon. Move around with a fork or chopstick until all the noodles separate from one another. Quickly add the bok choy, and allow to sit for 10 seconds. Then drain the noodles and bok choy, and set aside.
2. Marinate pork with 1 tsp sugar, 2 teaspoons soy sauce, a pinch of salt, and freshly cracked black pepper. Set to the side.
3. Heat a large wok on medium-high heat and add 1 tbsp of vegetable oil. Once hot, add onions, stir-fry until tender crisp (15-30 seconds) and then remove from pan. Then add pork and stir-fry until cooked through and browned on the outside. Remove the pork from wok and transfer to a bowl
4. Add remaining 1 tablespoon of vegetable oil to wok and add in garlic and black pepper. Quickly fry ensuring not to brown the garlic. Then add in udon and bok choy, followed by 2 teaspoons of sugar, 1/4 cup soy sauce, and salt to taste. Increase heat to high, and quickly stir fry to coat all the noodles, just until the soy sauce has slightly evaporated. Then add in pork and onions, and mix to combine. Drizzle in sesame oil, and stir once more to coat.