For the crust:.
In a nine-inch spring form pan, mix the cracker crumbs and the melted butter. Press the crumb mixture into a crust across the bottom and about one inch up the sides.
Bake for 8 minutes at 350°.
For the filling:.
In a microwave bowl, melt chocolate until smooth. Set aside. In a large mixing bowl, combine cream cheese, sugar, sour cream, and vanilla; beat with a mixer until smooth. Add flour 1 tablespoon at a time, blending well after each addition. Add eggs and melted chocolate; blend well. Pour into crust.
Bake 10 minutes without opening oven door at 425°(450° if using a light colored spring-form pan). Reduce oven to 225° (250° if using a light colored spring-form pan) and continue baking 35 - 45 minutes or until center is set. Remove from oven. With knife loosen sides and cool completely. Remove from pan.
Spread topping on top and refrigerate until firm. Store uneaten portion covered, in refrigerator.
For the topping:.
In small microwave-safe bowl, beat egg yolks. Stir in sugar, butter and whipping cream. Microwave on HIGH power 4 minutes, stirring every minute. Remove from microwave and stir in vanilla extract. Stir in coconut and pecans until well blended. Refrigerate until mixture is of spreading consistency. Spread on top of the cheesecake.
Optional: Drizzle topping with 1/4 cup semi-sweet chocolate chips melted with 1 teaspoon vegetable shortening. Place mixture in Baggie and snip corner with scissors to drizzle over cheesecake.