2 1/2 cups strong black coffee, room temperature
1 1/2 tablespoons espresso powder
9 tablespoons dark rum
2 tablespoons vanilla extract
6 large egg yolks
2/3 cup sugar
1/4 teaspoon table salt
1 1/2lbs mascarpone cheese (chilled below room temperature)
3/4 cup heavy cream, cold
14oz hard ladyfingers (about 40-60 depending on size)
3 /12 tablespoons cocoa
1/4 cup semisweet or bittersweet chocolate
Stir together coffee, espresso powder, vanilla extract, and 5 tablespoons rum in a wide bowl or baking dish until espresso dissolves. Set aside.
In a large bowl, beat together the yolks until just combined. Add sugar and salt and whisk together until a pale yellow, making sure to scrape down the sides of the bowl. Add the remaining 4 tablespoons rum and beat until just combined. Add the mascarpone and continue to beat until no lumps remain.
In another large bowl, beat the cream hard until the cream begins to hold stiff peaks. Using a rubber spatula, fold one-third of the whipped cream into the mascarpone mixture to lighten. Fold the remaining whipped cream into the mascarpone until there are no more white streaks.
Working one at a time, quickly drop half of the ladyfingers into the coffee mixture, roll, then remove and transfer them to a 9″x13″ baking dish. (Don’t submerge the ladyfingers. You want them to take in a little of the coffee mixture, but not drown in it. The coffee should coat the edges but not be soaked into the middle.
Arrange the cookies in a single layer in the baking dish, breaking or trimming the ladyfingers as needed to fit properly.
Spread half the mascarpone over the ladyfingers, and use a rubber spatula to spread the mixture to the edges and corners.
Place 2 tablespoons of the cocoa in a fine mesh strainer and dust the cocoa over the mascarpone.
Repeat the dipping and arrangement with the remaining ladyfingers, mascarpone, and remaining cocoa. Cover the dish with plastic wrap and refrigerate at least 6 hours before serving.