Cook couscous according to package directions, omitting salt and fat.
Combine cumin and next 4 ingredients (through pepper) in a bowl; stir in 1/4 teaspoon salt. Sprinkle spice mixture over chicken. Heat a large nonstick skillet over medium heat. Coat pan with cooking spray. Add chicken to pan; cook 6 minutes on each side or until done.
Combine remaining 1/4 teaspoon salt, chopped cilantro, garlic, and yogurt in a bowl, stirring well. Serve with chicken and couscous. Garnish with cilantro sprigs, if desired.