These golden mini turnovers are filled with guava paste, which can be found in the Hispanic sections of supermarkets.
In the bowl of a food processor, combine flour, baking powder, and salt. Add butter and pulse until dough resembles coarse crumbs, about 30 seconds. Add milk and pulse until dough comes together into a ball. Flatten dough into a disk, wrap in plastic wrap, and refrigerate at least 30 minutes.
Preheat the oven to 375°. Roll dough out on a lightly floured surface to a 16x16-inch square of about ⅛-inch thickness. Cut dough into 16 four-inch squares.
Whisk egg and water in a small bowl, then use a pastry brush to paint the edges of each square with the egg mixture. Place 1-½ teaspoons guava paste or preserves and ¾ teaspoon cream cheese into the center of each square. Mash together lightly with a fork. Fold the edges of the dough over to create a triangle shape, firmly pinch the edges of the triangle together so the filling won’t leak out during baking, then fold edges over.
Place the empanadas on a greased baking sheet and brush with egg wash. Prick each empanada gently with a fork to allow steam to escape. Bake 20 to 25 minutes, or until golden brown. Allow to cool slightly, then serve warm. Sprinkle with confectioners’ sugar, if desired.