Combine condensed milk and butter for filling in a pot over medium-low heat. Simmer, stirring occasionally, until it coats the back of a spoon and becomes caramelized, about 2 hours.

While the filling is simmering, mix flour, butter, powdered sugar, pisco, baking powder, and salt for cookies in a stand mixer fitted with the paddle attachment until a dough forms.

Shape dough into a disc and wrap in plastic wrap. Refrigerate for 15 to 30 minutes.

Preheat the oven to 350°F (175°C). Line 2 baking sheets with parchment paper.

Roll dough on a lightly floured surface to a thickness of 1/8 inch or 3/16 inch. Use a small cookie cutter to cut approximately 80 circles. Transfer cookies to the prepared baking sheets; prick each cookie once with the tines of a fork.

Bake cookies in the preheated oven until edges are just golden, about 12 minutes, switching racks halfway through; do not let them brown. Remove from oven and transfer to a wire rack. Repeat to cook remaining cookies.

When the filling has finished simmering, let it cool slightly, about 15 minutes.