Heat oven to 350 F. Line a 9-by-13 baking pan with parchment paper and grease with a nonstick cooking spray.

In a double boiler or a medium heatproof bowl placed over a gently simmering pot of water, melt chocolate, butter, cocoa and sugar together until mostly smooth. Turn off the heat, stir until completely smooth and fully melted.

Whisk in the eggs, one at a time, then vanilla, espresso powder and cardamom and salt.

Stir in flour with a spoon and scrape batter into prepared pan, spreading until even.

Bake for 30-35 minutes, or until a toothpick inserted into the center comes out batter-free.

While the brownies bake, make the caramel: Melt the sugar over medium to moderately high heat in a 2-quart pot, stirring the sugar as it melts to ensure it heats evenly.

Cook the liquefied sugar to a copper color. Add the butter and stir until the butter melts. Lower the heat and slowly drizzle in the heavy cream, whisking the whole time.

Remove from the heat and stir in the cinnamon and salt. Set aside until needed.

Cut the brownies into 16 or 32 squares and serve with cinnamon caramel sauce drizzled over the top. Sprinkle with flaky sea salt, if desired.