In a large bowl, sift together the flour, cocoa powder, sugar, salt and baking powder.
Use a pastry cutter or your fingers to work the butter and cream cheese into the flour mixture until it resembles pea-sized crumbs.
Add 2 tablespoons of the cold water to the mixture. Stir gently just until the dough comes together.
Turn the dough out onto a lightly floured surface. Fold the dough over onto itself a couple of times. Form the dough into a disk. Cover with plastic wrap and chill for at least 1 hour.
In a small microwavable bowl, melt the chocolate chips and sweetened condensed milk in the microwave. Heat for 10 second intervals, stirring until smooth.
Set aside to cool to room temperature.
Preheat the oven to 375ºF. Line a large baking sheet with parchment paper.
In a small bowl, whisk together the egg and remaining 1 tablespoon water.
On lightly floured surface, roll the dough to 1/8-inch thickness.
Cut out 20 rounds with a 2 3/4-inch circle cutter (or cut into desired shapes of your choice).
Place 10 dough rounds about 1 inch apart onto prepared baking sheet. Top each with 1 tablespoon of filling.
With a small pastry brush or your finger, brush egg mixture around the perimeter of each of the filled dough circles.
Top each with the 10 remaining dough circles. Crimp the edges together with a fork. Brush the pies with the remaining egg mixture.
Bake until the crust is crisp and browned, about 15-20 minutes.
Transfer to a cooling rack. Sprinkle the cooled pies with powdered sugar or drizzle with melted white chocolate.
*The chocolate chips you use depends on personal preference. Bittersweet chocolate chips give a more intense chocolate flavor, while semi-sweet chocolate chips yield a slightly sweeter finished product.