Preheat oven to 350 degrees F. In a large bowl, with an electric beater on medium speed, beat cream cheese and 1/2 cup sugar until well blended. Add 2 eggs one at a time, mixing well after each addition. Blend in the melted chocolate and 1 teaspoon vanilla then pour mixture into pie crust. Bake 35 to 40 minutes, or until firm; let cool 15 to 20 minutes.
In a small bowl, whisk remaining egg until lightly beaten. Place in a small saucepan and add evaporated milk, butter, and the remaining 1/3 cup sugar and 1/2 teaspoon vanilla; heat over medium-low heat 12 to 15 minutes, or until thickened, stirring constantly. Stir in coconut and chopped pecans; let cool. Spread over the top of the cheesecake; cover and chill 4 to 6 hours before serving.