
1¼ cups plus 1 tablespoon unsalted butter, divided
¾ cup all-purpose flour
¾ cup unsweetened Dutch-process cocoa powder
1 teaspoon instant espresso powder
1 teaspoon coarse kosher salt
3 large eggs, at room temperature
¾ cup granulated sugar
½ teaspoon vanilla extract
¾ cup semisweet chocolate baking chunks
Powdered sugar, for dusting