In a screaming hot cast iron skillet, sear the quickly sear pork pieces on all sides, stirring briskly for 4-6 minutes until the pieces start to brown and caramelize a bit. (this step can be omitted, but I think it really adds to the flavor)
Fifteen minutes before serving, cook the soba noodles for 2½ minutes, adding the bell peppers and snow peas to the water during the last 60 seconds of cooking, stirring gently. Drain, dump into a colander and run under cold water to stop the cooking. This will prevent the noodles from getting gummy.
Transfer the pork to a medium bowl and set aside. Pour the cooking liquid into a large skillet and boil until slightly thickened, 4 to 5 minutes. Add the pork and toss to combine.
Warm a portion of the noodles and vegetables briefly in a microwave or just toss quickly in a hot pan. Serve the pork over the noodles and vegetables; sprinkle with the peanuts and scallions.
NOTE: It's not mandatory to sear the pork. You can skip to Step 2 and just add the raw cubes to the slow-cooker and it will still taste great.