For the Pie Crust:

1. Prepare the Pie Dough:
   • In a large bowl, combine the flour, salt, and sugar (if using). Add the cold, cubed butter and use a pastry cutter or your fingers to cut the butter into the flour until the mixture resembles coarse crumbs with pea-sized pieces of butter.
   • Gradually add the ice water, one tablespoon at a time, and mix until the dough begins to come together. Add more water if necessary.
2. Chill the Dough:
   • Form the dough into a disc, wrap it in plastic wrap, and refrigerate for at least 30 minutes to allow it to firm up.
3. Roll Out the Dough:
   • After the dough has chilled, roll it out on a floured surface until it’s about 1/8 inch thick. Cut out circles (about 5 inches in diameter) and gently press them into a muffin tin or individual pie tins.
4. Bake the Crust:
   • Preheat your oven to 375°F (190°C). Line the pie crusts with parchment paper and add pie weights or dried beans to keep them from puffing up. Bake for 10-12 minutes, then remove the parchment paper and weights and bake for another 5 minutes until golden and fully cooked. Let them cool while you make the filling.

For the Chocolate Filling:

1. Make the Chocolate Custard:
   • In a medium saucepan, whisk together the milk, heavy cream, granulated sugar, cocoa powder, cornstarch, and salt. Heat the mixture over medium heat, whisking constantly, until it begins to simmer and thicken.
2. Temper the Eggs:
   • In a separate bowl, whisk the egg yolks. Gradually pour a small amount of the hot milk mixture into the eggs while whisking constantly to temper them (this prevents curdling).
3. Combine and Cook:
   • Slowly pour the egg mixture back into the saucepan with the remaining milk mixture, whisking constantly. Continue cooking over medium heat for 3-5 minutes, until the custard has thickened to a pudding-like consistency.
4. Add Chocolate and Butter:
   • Remove the saucepan from the heat and stir in the chopped chocolate, butter, and vanilla extract until the chocolate has melted and the filling is smooth and glossy.
5. Fill the Pies:
   • Pour the chocolate filling into the cooled pie crusts. Let them cool at room temperature for 15-20 minutes, then refrigerate for at least 2 hours or until the filling is set.

For Topping:

• Once the pies have cooled and set, top them with whipped cream, chocolate shavings, or a dusting of cocoa powder.