Whisk cream and coffee liqueur together in a medium bowl. Sift in powdered sugar and whisk until soft peaks form. Chill.
Stir chocolate sauce and espresso together in a small saucepan over medium heat. Cook, stirring, until warmed through. Stir in rum and reduce heat to low.
Put 3 scoops ice cream on each of 4 plates and top with whipped cream. Spoon a thick band of chocolate sauce along the side of the plate. Scatter plates with toasted macadamia nuts, cookies, and cacao nibs, if using.
*Cacao nibs are available on amazon.com