Adapted from Bon Appetit
Divide scallions into two bunches. You'll use about 4 scallions for the chili oil, and keep the rest raw to toss in at the end. For the first bunch, chop whites horizontally until small. For the second bunch, slice green parts vertically, as thinly as possible, and set aside.
Place a small saucepan over medium-high heat. Add canola oil, sambal olek, and 3 tablespoons toasted sesame oil. Once oil mixture is hot, add minced garlic, chopped scallion whites, and sesame seeds. Lower heat to medium and simmer, stirring frequently to avoid burning, for 6-8 minutes. Remove from heat and let cool.
Meanwhile, cook soba noodles according to package instructions. Drain, rinse, and set aside.
In a medium-sized bowl, whisk together tahini, rice vinegar, soy sauce, sugar and remaining 1/4 cup toasted sesame oil. Add in cooled chili oil, whisking to combine.
Combine noodles with sauce and bell pepper and toss to coat.
Serve noodles on a bed of greens (I prefer a spicy mix like arugula and baby kale, but spinach would work well here too).
Top with sliced scallion greens and diced avocado.