In a medium bowl, beat the heavy whipping cream, powdered sugar, salt, and instant espresso powder with an electric mixer until soft peaks form.

In another bowl, stir the mascarpone cheese with vanilla extract until smooth. Then gently fold the whipped cream into the mascarpone until well blended. Be careful not to overmix.

Quickly dip each halved ladyfinger into the coffee mixture (1-2 seconds) and place a layer (2 halves) at the bottom of each serving cup. Top with a spoonful of the mascarpone cream and repeat the layers until the cups are filled, using 4 ladyfinger halves per serving cup.

Cover the cups with plastic wrap and refrigerate for at least 2 hours. Just before serving, dust the tops with unsweetened cocoa powder. Garnish with chocolate shavings if desired.