Although we've provided a spice mix for blackening the chicken, there are several commercial mixes you can use but be forewarned: They are high in salt. If you like your food hot, try Paul Prudhomme's Magic Seasoning line. If you prefer it mild, try McCormick's Cajun Seasoning mix.
Combine the first 7 ingredients in a bowl, and toss well. Cover and chill.
Combine lemon juice, mustard, water, and honey in a large bowl; stir well with a wire whisk. Cover and chill.
Rub chicken with Spicy Seasoning. Coat a large heavy skillet with cooking spray, and place over medium-high heat until hot. Add chicken, and cook 7 minutes on each side or until chicken is done. Remove chicken from skillet, and let cool. Cut chicken across grain into thin slices, and set aside.
Steam snap peas, covered, for 2 minutes. Rinse under cold water, and drain. Add snap peas and lettuce to the lemon juice mixture, and toss well. Divide the lettuce mixture evenly among 4 large salad bowls; top each serving with 1 cup of the tomato mixture and 1 sliced chicken breast half. Garnish with parsley sprigs, if desired.