Preheat oven to 375. Arrange chicken in 13x9x2 baking dish, and sprinkle with mustard, cumin, coriander, and hot red pepper. Spray onion with Pam, spoon around chicken. Bake uncovered 50 minutes, until chicken is browned, stirring onions occasionally.
Meanwhile, spray Pam in large frying pan over medium heat. Add walnuts, cook 2-3 minutes, stirring constantly, until lightly toasted. Sprinkle with ginger and sugar. Cook, stirring, until sugar melts. Add soy sauce and cook, stirring, until liquid evaporates to a glaze. Remove from heat and let cool.
Heat Pam in same pan over medium heat. Add spinach and soy sauce. Stir fry until wilted and tender, set aside. Add nuts and sauce that is below.
In a small saucepan, combine vinegar, sugar, hot pepper, soy sauce, and water. Bring to a boil. Stir dissolved cornstarch slowly into hot sauce. Return to a boil, stirring, until thickened. Remove from heat, cover, and set aside. When chicken is done, stir sauce and kale into pan juices. Scatter walnuts on top. Return to oven for 5-10 minutes to heat through.