In large skillet, combine first 3 ingredients. Cook over medium heat until browned, stirring to crumble beef. In a saucepan, slowly heat spices in butter. Drain beef. Wipe skillet dry with a paper towel. Return beef mixture to skillet; add chopped spinach, spices and salt; stir well. Cover and cook over medium heat 5 minutes or just until spinach is wilted; remove from heat. Line each pita half with whole spinach leaves. Spoon half cup beef mixture into each pita half. Mix sour cream or yogurt with curry powder. Top each pita half with 1 tablespoon sour cream or yogurt.