Brew espresso ahead of time and chill; then stir in dark rum or coffee liqueur.

In a double boiler or metal bowl over simmering water, whisk together egg yolks and sugar for 10 minutes until thickened. Remove from heat.

Using an electric mixer, beat the yolk mixture until pale and smooth. Add mascarpone and fold to combine.

In another chilled bowl, whip 1¾ cups heavy cream with cream of tartar and vanilla until stiff peaks form; gently fold into the mascarpone mixture without streaks.

Dip ladyfingers quickly into espresso, then arrange a single layer in a large trifle bowl.

Spread half the tiramisu cream over the soaked ladyfingers.

Repeat layers with more dipped ladyfingers and the remaining cream.

Whip additional 2 cups of cream until stiff and spread on top. Dust with cocoa powder and finish with chocolate shavings.

Cover and refrigerate at least 8 hours or overnight before serving to set.