Chocolate and Vanilla Pudding Pie (Zebra Cream Pie)

Ingredients

• 1 prepared chocolate crumb crust ((I use store-bought))
• 2 ounces bittersweet chocolate
• 2 cups of milk
• 3/4 cup sugar
• 1/3 cup flour
• 1/8 teaspoon salt
• 3 large egg yolks
• 1 tablespoon butter
• 1 teaspoon vanilla extract
• 1 cup cold heavy cream
• 2 tablespoons powdered sugar
• finely-chopped chocolate for garnish (optional)