Whisk the egg yolks with the sugar in a glass bowl until the mixture is light and fluffy. Add the flour, then the grated lemon peel, milk, fresh cream and rum.
Put the mixture in a saucepan and cook over a low heat and stirring with a wooden spoon until the cream becomes thick and full-bodied. Then remove the saucepan from the heat, put the rum cream in a glass bowl and let it cool.Cut the pandoro into slices about 2 cm thick.
Form a rectangle, placing the slices of pandoro, on a surface covered with parchment paper, side by side and filling the empty spaces with other bits of pandoro. Then lightly moisten the pandoro base obtained with a syrup of water, sugar, rum and a lemon peel.Coprite with a sheet of parchment paper and flatten it all with a rolling pin, so as to form a uniform base without empty spaces.Stuff now with the rum cream leveling the cream as much as possible.
Roll from the longest part, helping with the baking paper to form a roll.

Once the roll has been formed, wet the surface a little with the advanced wets, then wrap it in the foil and place in the fridge to harden for an hour.

Now remove the film and cut off both ends. Cover the pandoro roll with icing sugar and decorate with melted chocolate, then transfer it gently onto a serving tray and serve.