Whisk the cream until whipped and firm. Refrigerate.
Melt the white chocolate in a double-boiler or in the microwave. Set aside.
Grate the zest of the orange.
Cut the orange in half and squeeze the juice out.
Cut the vanilla bean lengthwise and scrape off the seeds.
In a mixing bowl, place the mascarpone cheese, the sugar, egg yolks, vanilla seeds, the juice and zest of the orange, and the cubes of candied orange. Mix together until well combined.
With a spatula, pour half of the whipped cream into the cheese mix.
Fold the mix gently. Pour the other half into the cheese mix.
Place half the biscuits in a 25 cm (9 in.) square pan.
Pour evenly onto the layer of biscuits, following this order, half of the espresso, half of the Cointreau, half of the white chocolate, half of the cheese mix.
Spread well all over the biscuit surface.
Place the rest of the biscuits on top, and repeat the previous step with the rest of the espresso, Cointreau, chocolate, and cheese mix.
Cover with plastic wrap and refrigerate for at least 4 hours before serving.
When ready to serve, sprinkle cocoa powder over the tiramisu.