Preheat oven to 350°F (180°C).

In the top of a double boiler, combine chocolate and butter. Cook over simmering water, stirring occasionally, until melted and smooth. Remove from heat, and whisk in sugars until well combined. Let cool slightly, 1 to 2 minutes.

In a medium bowl, whisk together flour, cocoa, salt, and espresso powder.

Gradually add eggs to chocolate mixture, whisking until combined. Whisk in vanilla. Fold in flour mixture just until combined. Spread batter into cold Chocolate Chip Cookie Crust.

Bake until a wooden pick inserted in center comes out with a few moist crumbs, 55 minutes to 1 hour and 5 minutes. Let cool completely on a wire rack. Serve with whipped cream. Store in an airtight container for up to 3 days.