COMBINE rice, 1-1/2 cups milk, sugar and salt in a heavy saucepan. COOK over medium heat, stirring occasionally for 15 to 20 minutes until thick and creamy. BLEND remaining 1/2 cup milk and egg; stir into rice mixture. STIR in raisins. COOK an additional 2 minutes, stirring constantly. STIR in butter and vanilla and spoon into serving dishes. Sprinkle with nutmeg or cinnamon, if desired.