How to Make It
Make the crust Preheat the oven to 350°. Brush a large rimmed baking sheet with melted butter. Line the baking sheet with parchment paper, leaving a 1-inch overhang.
In a large bowl, using your fingers, combine the flour with the brown sugar and salt. Drizzle in the 4 sticks of melted butter and stir with a fork until a lumpy dough forms. Press the dough evenly over the bottom and up the sides of the prepared baking sheet. Refrigerate until firm, about 15 minutes.
Line the pie shell with parchment paper and fill to the top with pie weights or dried beans. Bake in the center of the oven for about 20 minutes, until lightly browned. Remove the pie weights and parchment paper. Transfer the crust to a wire rack to cool, about 1 hour.
Meanwhile, make the filling Reduce the oven temperature to 325°. In a heatproof medium bowl set over a saucepan of simmering water, melt the diced butter with the chocolate chips, stirring occasionally, until smooth, about 3 minutes. Stir in the vanilla and remove the bowl from the heat. Whisk in the granulated sugar, espresso, cinnamon and salt until blended. Whisk in the eggs, one at a time. Pour the filling into the cooled crust. Bake for about 45 minutes, until the center is set and the top begins to crack. Transfer the pie to a wire rack to cool completely, about 2 hours.
Cut the pie into 2-inch-square bars. Dust the top with confectioners’ sugar and serve.