Whisk together soy sauce, sesame oil, olive oil, vinegar, peanut butter, cayenne pepper, ginger, garlic, and serrano in a small bowl; set aside.
Toast spelt kernels in a dry skillet on medium-high heat until the kernels are browned and some have popped. Remove, place in a mesh strainer, and rinse well with cold water. Drain. Bring 6 cups of water to a boil in a large saucepan; add 1/2 teaspoon kosher salt and stir in spelt kernels. Return to a boil then cover, reduce heat to low, and simmer until tender, about 1 hour. Drain well and set aside to cool.
While the spelt is simmering, fill a skillet with 1 quart water, 1/2 teaspoon salt, and onion. Bring to a boil over high heat. Add chicken breasts, reduce the heat to medium-low, cover, and simmer until the chicken is cooked through, about 15 minutes. Remove chicken from liquid and allow to cool.
Once chicken is cool enough to handle, shred into bite-sized chunks and place in a large bowl. Stir in spelt, bell pepper, green onions, parsley, cilantro, carrots, and cabbage. Pour sauce over salad and stir well to combine.