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  1. Preheat the oven to 375°F. Lightly grease a 13 ¾" x 4 ½" rectangular tart pan; or an 8" square pan, or 9" round pan. If you're using an 8" square or 9" round pan, it's best to line the pan with parchment and grease the parchment, to facilitate turning the cake out of the pan without crumbling.

  2. Heat the chocolate and butter together, stirring frequently, until melted. This can be done in a double boiler (bain-marie), with a microwave, or on a burner set over low heat. Transfer to a mixing bowl.

  3. Add the sugar, salt, and espresso powder.

  4. Add the eggs, beating briefly until smooth.

  5. Add the cocoa powder, and mix just to combine.

  6. Spoon the batter into the prepared pan.

  7. Bake the torte for 22 to 25 minutes. Remove it from the oven, and cool it in the pan for 5 minutes. Loosen it from the edges of the pan, and turn it out onto a serving plate. Allow the cake to cool completely.

  8. To make the ganache filling, heat the cream until it just begins to simmer. Remove it from the heat, and add the chocolate, stirring until the mixture becomes smooth. Allow the ganache to cool to room temperature.

  9. Spread half the ganache evenly over the top and sides of the tart. Scoop out teaspoon-sized bits with the remaining ganache, place on parchment or waxed paper, and chill for 1 hour.

  10. Shape the ganache bits into balls, and roll them in cocoa powder to make truffles. If you have a variety of cocoa powders, use them all, for prettiest presentation. Decorate the torte with the truffles as desired.