1. Stir co ee, espresso, and 5 tablespoons rum in wide bowl or baking dish until espresso dissolves; set aside
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1. Stir coffee, espresso, and 5 tablespoons rum in wide bowl or baking dish until espresso dissolves; set aside
2. In bowl of standing mixer fitted with whisk attachment, beat yolks at low speed until just combined. Add sugar and salt and beat at medium-high speed until pale yellow, 1 1/2 to 2 minutes, scraping down bowl with rubber spatula once or twice. Add remaining 4 tablespoons rum and beat at medium speed until no lumps remain, 30 to 45 scraping down bowl once or twice. Transfer mixture to large bowl and set aside.
3. In now-empty mixer bowl (no need to clean bowl), beat cream at medium speed until frothy, 1 to 1 1/2 minutes. Increase speed to high and continue to beat until cream holds stiff peaks, 1 to 1 1/2 minutes longer. Using rubber spatula, fold one-third of whipped cream into mascarpone mixture to lighten, then gently fold in remaining whipped cream until no white streaks remain. Set mascarpone mixture aside.
4. Working one at a time, drop half of lady fingers into coffee mixture, roll, remove, and transfer to 13 by 9-inch glass or ceramic baking dish. (Do not submerge lady fingers in coffee mixture; entire process should take no longer than 2 to 3 seconds for each cookie.) Arrange soaked cookies in single layer in baking dish, breaking or trimming lady fingers as needed to fit neatly into dish.
