Make the salad: Bring a medium pot of salted water to a boil; add the noodles and cook as the label directs. Drain, then toss with the soy sauce and sesame oil in a large bowl; cover and chill until needed.
Bring a large pot of salted water to a boil. Reduce the heat to medium low, add the chicken and simmer until cooked through, about 10 minutes. Drain and shred the chicken; set aside.
Heat a wok or medium skillet over medium-high heat. Cook the cashews, stirring, until browned, about 3 minutes. Let cool slightly, then place in a plastic bag and bash with a rolling pin.
Make the peanut sauce: Heat the wok over high heat and add the peanut oil. Add the shallots and fry until translucent, about 45 seconds; add the peanut butter and jalapeno and stir-fry less than 1 minute. Stir in the vegetable broth and 3 tablespoons water. When the sauce starts to bubble, remove from the heat and transfer to a bowl. Season with salt. (If you like your sauce thinner, stir in a few tablespoons of water.)
Assemble the salad: Divide the noodles, jalapeno, cucumber, bean sprouts, cilantro and scallion among bowls; top with the shredded chicken. Drizzle with the peanut sauce and sprinkle with the crushed cashews.