Preheat oven to 350 degrees F (175 degrees C.) In the top of a double boiler, heat chocolate, stirring occasionally, until chocolate is melted and smooth. Remove from heat and allow to cool to lukewarm.
In a large bowl, beat the cream cheese, sugar and vanilla until smooth. Slowly beat in eggs, one at a time. Blend in melted chocolate. Pour filling into crust.
Bake in the preheated oven for 40 minutes, or until filling is set. Allow to cool. Refrigerate for at least 3 hours before serving.