Place the 24 ladyfinger cookies in a food processor and process until fine crumbs form, about 1 minute. (No food processor? No worries! Simply place the lady fingers in a ziploc bag and gently roll over with a rolling pin — the cookies are delicate enough that they'll easy crumb up.) Set aside.
In a medium bowl, whisk together 1/2 cup granulated sugar, 2 teaspoons vanilla extract, 1 cup mascarpone cheese, 1/4 cup brewed espresso until the ingredients are evenly distributed and there are no lumps in the mixture. The mixture will have the consistency of sweetened condensed milk — it will seem like its too thin, but it's fine. Trust the recipe!
Spoon a tablespoon of ladyfinger crumbs into each ramekin, before topping off with a tablespoon of the sugar, mascarpone, and espresso mixture (from the second step). Repeat until you've finished both the crumbs and cream mixture, making sure to finish the top of each ramekin with the sugar, mascarpone, and espresso mixture. You should have two layers of each mixture in each ramekin.
Refrigerate for at least 3 hours, preferably overnight. Just before serving, whisk together 2 tablespoons cocoa powder and 4 teaspoons ground cinnamon in a small bowl. Sprinkle over each ramekin just before serving.