Whisk: In a large mixing bowl, whisk together egg yolks and sugar.
Create a double boiler: Fill a small pot with about 1" of water. Bring it to a boil. Turn off the heat and place the mixing bowl with the egg yolk mixture on top of the pot, ensuring the bottom of the bowl doesn't touch the water.
Heat egg mixture: Whisk the egg yolk mixture until most of the sugar has dissolved and the mixture becomes warm, fluffy, and pale in colour, about 5-7 minutes. Remove the bowl from the pot.
Add mascarpone: Immediately add the mascarpone cheese to the warm egg mixture. Whisk until the mascarpone cheese has completely melted into the mixture without any lumps. Set aside.
Whip cream: In another large mixing bowl, add whipping cream and vanilla extract. Use an electric hand mixer to beat the cream until it becomes firm peaks.
Combine whipped cream and mascarpone mixture: Add the whipped cream to the mascarpone mixture. Fold together with a spatula until no streaks remain. Set aside.
Prepare soak: In a wide but shallow bowl, stir together mango juice and rum.
Soak ladyfingers: Dip each ladyfinger briefly (1 second per side) into the juice mixture to coat both sides. Arrange the soaked ladyfingers on the bottom of your container.
Add layers: Add half of the mascarpone cream on top of the ladyfinger layer. Use a spatula to smooth it into an even layer. Add a layer of diced mangoes and press them into the cream.
Repeat: Repeat soaking ladyfingers and arranging another layer on top of the mango layer. Top with the remaining mascarpone cream and smooth with a spatula. To make a flat top, scrape the excess cream off with a bench scraper. Repeat with your other containers if you're making multiple small servings.
Pipe cream (optional): Transfer the remaining mascarpone cream to a piping bag fitted with an open star piping tip. Pipe the cream on top of each tiramisu. Garnish with extra mango chunks.
Chill: Chill the mango tiramisu in the fridge for at least 6 hours or preferably overnight before serving.