Heat oven to 375 degrees.Melt butter over low heat;add cocoa and stir until smooth.Remove from heat;cool slightly.Stir in sugar, salt,eggs and corn syrup.Blend thoroughly.Stir in chopped nuts,if desired.Pour into unbaked pie shell.Place pecan halves over top.Bake for 40 minutes.Cool.Let stand 8 hours before serving.Garnish with sweetened whipped whipping cream or whipped topping.Makes 8 servings.