Bring a pot of water to a boil and cook the soba noodles according to package directions, adding the chopped baby bok choy during the last 60 seconds of cooking.
Drain the noodles and bok choy, reserving 2 tablespoons of the hot cooking water for the sauce.
In a small bowl, whisk together the tahini, tamari, chili oil, toasted sesame oil, rice vinegar, and the reserved cooking water until the sauce is smooth and creamy.
Heat a large non-stick skillet over medium-high heat and add the ground pork, breaking it into small crumbles with a spatula until browned and fully cooked.
Add the minced fresh ginger, minced garlic, and ground Sichuan peppercorns to the skillet with the pork and sauté for 1 minute until highly fragrant.
Add the cooked soba noodles and bok choy to the skillet, tossing them with the pork mixture to combine.
Pour the prepared sesame-chili sauce over the noodles and pork, tossing continuously until every strand is evenly coated and the sauce is warmed through.
Divide the mixture into a bowl and garnish with the freshly sliced green onions before serving.