Set steamer basket in a large pot; add water to within 1/4 inch of bottom of basket.
Bring water to a boil over high heat. Layer about1/4 of the spinach in basket; cover and steam 15 seconds. QUickly turn leaves over with tongs. Cover and steam 15 seconds more (or until leaves are bright green and barely wilted).
Transfer spinach to colander. Repeat with remaining spinach. Lay spinach on serving platter or individual plates.
Bring 6 cups of water to a boil in a large saucepan over high heat. Add chicken to boiling water; remove saucepan from heat. Let stand, covered, 5 minutes or until chicken is no longer pink in center.
Prepare Peanut Sauce.
Heat oil in medium saucepan over medium-high heat. Add onion and garlic; cook and stir 2 to 3 minutes or until tender.
Reduce heat to medium. Add peanut butter, fish sauce, paprika, cayenne and red pepper flakes; stir until smooth. Slowly stir in coconut milk until well blended. (at this point, cause may be cooled, covered and refrigerated up to 2 days in advance).
Stir sauce constantly over mdium heat until bubbling gently. Reduce heat to medium-low. Combine cornstarch and water in a small cup; stir into sauce. Cook and stir 1- to 2 minutes or until sauce is thickened. Stir in lime juice.
Drain chicken; stir into hot Peanut sauce. Pour mixture over spinach. Top with chopped peanuts and reserved red chili pepper.