In a shallow bowl, whisk together ¼ cup of Dutch processed cocoa powder and 1 cup of cooled espresso until smooth. Optionally add dark rum.

In a stand mixer, combine 4 egg yolks with ½ cup of white sugar. Beat until pale and thick, then add a pinch of salt and 16 ounces of mascarpone cheese, whipping until smooth.

In a separate bowl, whip 1.75 cups of heavy cream until soft peaks form. Fold into the mascarpone mixture gently.

Dunk ladyfingers in the espresso mixture for 1-2 seconds and arrange in a 7x11-inch dish.

Spread half of the mascarpone mixture over the ladyfingers and dust with cocoa powder.

Repeat the dunking and layering with remaining ladyfingers and mascarpone mixture.

Dust with cocoa powder, cover with plastic wrap, and refrigerate for at least 2 hours before serving.