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 minute of cooking.
Drain the noodles and bok choy, then set aside.
In a large skillet over medium-high heat, cook the ground pork until browned and cooked through, breaking it into small crumbles as it sears.
Add the minced garlic, grated ginger, and crushed Sichuan peppercorns to the skillet, sautéing for 1 minute until highly fragrant.
In a small bowl, whisk together the tahini, tamari, chili oil, rice vinegar, and water to create a smooth, pourable sauce.
Pour the sauce into the skillet with the pork and stir to combine, allowing it to simmer for 1-2 minutes until slightly thickened and glossy.
Add the cooked noodles and bok choy to the skillet, tossing everything together until well-coated in the spicy sesame sauce.
Garnish the dish with thinly sliced green onions before serving immediately.