- ½ cup freshly-brewed coffee
- 8 oz semisweet chocolate, finely chopped
- 4 oz bittersweet chocolate, finely chopped
- 2 sticks unsalted butter
- 2 teaspoons instant espresso powder
- 1 teaspoon fine sea salt
- 1½ cups sugar
- 3 eggs
- 1 teaspoon vanilla extract
- ¾ cup all-purpose flour
- Preheat the oven to 350°F and lightly oil a 10-inch cast iron skillet (or 2-3 smaller skillets).
- In a small saucepan, heat the coffee to a simmer. Simmer until reduced by half, about 5 minutes. Set aside.
- In a microwave-safe bowl, place the butter and two kinds of chocolate. Heat for 30 seconds in the microwave, stir, and heat again in 30-second increments until the chocolate and butter are melted. Stir until smooth.
- Whisk the reduced coffee, instant espresso powder, sea salt, and sugar into the butter-chocolate mixture. Then, whisk in the eggs and vanilla until the mixture is thick, glossy, and smooth.
- Fold in the flour and mix until no lumps of flour remain.
- Pour the batter into the prepared skillet and bake until a toothpick comes out clean, about 35-40 minutes. Cool completely before slicing and serving, OR eat it warm straight from the skillet and topped with ice cream.