Combine 1 cup milk, sour cream and instant pudding mix. Mix on medium speed for 2 minutes, scraping sides.
In a small bowl, melt chocolate, butter and 1/4 cup milk on half power in the microwave. Stir until smooth and allow to cool slightly. (Add more milk if needed)
Gradually add 1/4 cup pudding mixture to the melted chocolate and blend using beaters till smooth. Repeat.
Pour the melted chocolate mixture into the pudding mixture and blend.
Fold in 1 cup cool whip. Fold into prepared pie crust.
Garnish with cool whip. You can add chocolate shavings, nuts or seasonal colored crushed chocolates on top of the cool whip if you choose.
Notes
Calorie count is an estimate and will vary based on ingredients and cooking methods used.