Tortesare richand dense, so a thin wedge is a perfect portion. Dip a long,sharp knife intowarm water,slice, and wipethe blade with a dish towel.
Preheat oven to 225 degrees. Butter an 8 1/2-inch springform pan; sprinkle with cocoa, and tap out excess. In a small bowl, combine currants and whiskey or hot water. Let macerate at least 10 minutes or up to 30 minutes. Strain currants in a fine sieve, and discard whiskey.
In a small saucepan over medium heat, bring cream and butter almost to a boil; making sure all butter is melted. Place chocolate in a medium heatproof bowl, and pour the cream over to cover. Whisk gently until chocolate is melted and mixture is combined.
In a medium bowl, whisk together the eggs, sugar, and salt. Whisk into chocolate mixture, and stir in nuts and currants. Pour mixture into prepared pan.
Bake until edges are set and center is still a little soft to the touch, about 2 hours. Transfer to a wire rack to cool completely. Cover with plastic wrap, and chill overnight in the refrigerator. When ready to serve, remove from refrigerator, and dust with cocoa powder.