Trim the pork shoulder of excess fat and chop it into smaller slices. Rub the five-spice powder and salt all over the meat.
Add the chicken broth, water, soy sauce, garlic, ginger, and meat into the slow cooker. Cook on high for 6 to 7 hours or on low for 8 to 9 hours.
When the pork is nearly done, take a small pot, and bring 2 cups of chicken stock and 2 cups of water to boil over medium-high heat. When the water is boiling, add the udon noodles into the pot. Let it cook for a few minutes before reducing the heat to medium-low. Add the miso, garlic powder, salt, and white pepper. Next, add the chopped green onions, saving about a tablespoon for garnish. Let the noodles cook for several more minutes, or until the noodles are soft and plump.
Using a fork, break up the pork, and serve it with the udon. I added a few tablespoons of the broth from the slow cooker to the noodles just to add a bit more flavor. Garnish the bowl with green onions, black sesame seeds, sprouts, cucumber, pickled daikon, or watermelon radishes if you like!
If you want a soupy noodle bowl, add more water when you’re cooking the noodles. Better yet, prepare more broth in a separate pot so that you can pour it over the noodles when you serve them.