After cooling, blend mascarpone with eggs. Heavy cream should form firm peaks when mixed with a handheld mixer in another basin. Carefully fold cream into egg-mascarpone mixture and set aside.
Ladyfingers may need to be trimmed with a sharp knife before dipping in espresso to fit in the pan. Pan bottom should hold 12 cookies.
Spread half the egg mascarpone mixture on ladyfingers using a rubber spatula. Continue layering ladyfingers and espresso, then egg mascarpone.
Wrap in plastic and chill for 4–24 hours. Pop off plastic wrap. Dust tiramisu with cocoa powder from a fine mesh sieve. Cut into 9 pieces and serve.