Set up a bain-marie by placing a heatproof bowl over a pan of simmering water, ensuring the water does not reach a boil or touch the bottom of the bowl.

Whisk the eggs and sugar in the bowl continuously until the mixture is thick, pale, and has tripled in volume.

Spread the mixture evenly onto a baking tray lined with parchment paper.

Bake in a preheated oven at 200°C (390°F); since the layer is very thin, it will cook rapidly, usually in about 10 minutes.

Remove the sponge with the parchment paper from the baking tray and roll it immediately while still warm to set the shape so it doesn't break.

Prepare the filling by first whisking the egg yolks with sugar until pale and creamy.

Gently fold in the mascarpone until smooth.

In a separate clean bowl, whisk the egg whites until stiff peaks form.

Gently fold them into the mascarpone mixture to create a light, fluffy cream.

Unroll the cooled sponge and spread the mascarpone cream evenly across the surface.

Roll the sponge back up tightly; if you prefer, you can lightly brush the sponge with orange liqueur, though I skip this for large family gatherings to keep the dessert child-friendly.

Frost the exterior with the marron mousse, using a fork to create textured lines that mimic the look of tree bark.

Garnish with candied cherries and caramelized orange and lemon zest, then refrigerate for several hours to allow the flavors to meld and the structure to firm up.