Preheat oven to 350 degrees, and grease 13x9 pan.
In a microwave-safe bowl, melt 8 Tbsp. butter with unsweetened chocolate.
In a mixing bowl, beat 2 eggs, sugar and vanilla. Add the chocolate mixture and mix until blended.
Slowly beat in the flour.
Spread into pan, and bake 15-20 minutes until top is set.
In a large mixing bowl, beat cream cheese and remaining 2 Tbsp. butter.
Add cornstarch and beat until smooth.
Gradually beat in condensed milk and remaining 1 egg.
Add peppermint extract and food coloring (if desired). Pour over crust.
Bake 15-20 minutes until center is almost set.
Cool on a wire rack.
In a heavy saucepan, combine chocolate chips and whipping cream.
Cook and stir over medium heat until chocolate chips are melted.
Cool for 30 minutes or until lukewarm, stirring occasionally.
Pour over cream cheese layer.
Chill for 2 hours or until set before cutting.