Preheat the oven to 325F.
Generously spray an 11"x7" (or similar--an 8"x8" pan will work, too). Set aside.
Melt the butter and chocolate together in a double boiler or in short bursts on medium power in the microwave. Stir until smooth and set aside.
In a medium bowl, whisk together the flour, chipotle powder, baking powder and salt. Set aside.
Whisk the sugar, eggs, espresso powder and Kahlua into the chocolate mixture until well combined.
Whisk in the flour mixture just until incorporated.