2 1/2 C strong, black coffee, room temperature
1 1/2 Tbsp espresso powder
9 Tbsp dark rum
2 Tbsp vanilla extract
6 large egg yolks
2/3 C sugar
1/4 tsp salt
1 1/2 lbs mascarpone cheese, chilled
3/4 C heavy cream, cold
14 oz. hard ladyfingers (40-60 depending on size)
3 1/2 Tbsp cocoa
1/4 C semisweet or bittersweet chocolate
Combine coffee, espresso powder, vanilla extract, and 5 Tbsp rum, in a wide bowl or baking dish, until espresso dissolves. Set aside.
In a large bowl, beat yolks until just combined. Add sugar and salt. Whisk until pale yellow, making sure to scrape down the sides of the bowl. Add remaining rum and beat until just combined. Add mascarpone. Beat until no lumps remain.
In another large bowl, beat cream until stiff peaks form. Using a rubber spatula, fold one third of cream into mascarpone, to lighten mixture. Fold in remaining cream until no white streaks appear.
Working one at a time, quickly drop half the lady fingers into coffee mixture, roll over, and transfer to a 9x13 baking dish. Do not submerge. The coffee should coat the edges, but not be soaked in to the middle.
Arrange in a single layer, breaking or trimming the ladyfingers, as needed, to fit properly.
Spread half the mascarpone over the ladyfingers. Use a rubber spatula to spread the mixture to the edges and corners.
Place 2 Tbsp cocoa in a fine mesh strainer. Dust cocoa over mascarpone.
Repeat dipping with the remaining ladyfingers, mascarpone, and remaining cocoa.
Cover with plastic wrap and refrigerate at least 6 hours before serving.