In a small bowl, whisk cream, espresso powder, and cocoa until smooth.
In the large bowl of a stand mixer fitted with the paddle attachment, beat mascarpone, cream cheese, and confectioners’ sugar on medium-high speed until smooth, about 2 minutes. Scrape down bowl. Add cream mixture, vanilla, and salt. Beat on low speed until just combined, then increase speed to medium-high and beat until light and fluffy, about 1 minute more.
Transfer dip to a serving bowl. Dust with more cocoa powder. Serve with ladyfingers alongside.
