Bring 1 cup of water to a boil in a medium saucepan. Stir in couscous, and cover and remove from heat. Let stand 5 minutes. Fluff with a fork.
While couscous cooks, combine 1/2 cup water, coconut milk, and next 6 ingredients (through curry paste), stirring well with a whisk.
Heat 1 teaspoon oil in a large nonstick skillet over medium-high heat. Sprinkle chicken with 1/4 teaspoon salt. Add chicken to pan; cook 6 minutes or until done, turning once. Remove from pan; keep warm.
Add remaining 1 teaspoon oil to pan. Add peas, onion, and mushrooms; cook 3 minutes or until mushrooms are tender. Add coconut milk mixture and 1/4 teaspoon salt to pan; bring to a boil. Reduce heat, and simmer 1 minute. Add chicken and lime juice to pan; cook 1 minute or until thoroughly heated. Serve over couscous; garnish with lime wedges, if desired.