Preheat oven to just under 400 °F (200 °C).

Roll out the prepared puff pastry dough about 3mm thick and cut into two bases (about 12x18in (30x45 cm) each).

Lay the dough on a baking sheet, stipple with a fork (poke gently several times), and bake for 10 minutes.

Warm apricot marmalade with some rum and brush on the puff pastry bases.

For the vanilla cream, boil half the milk with granulated sugar and vanilla sugar.

Mix the other half of the milk with vanilla pudding mix until smooth and then stir into the boiling milk.

Bring to a boil again and then remove from heat.

Add cold water to the gelatin, remove excess water, and dissolve in the still-hot vanilla mixture.

Stir in rum and chill, but do not let it gel completely.

Fold whipped cream into the cooled vanilla cream.

Place the puff pastry base in a loaf pan or baking frame, spread the vanilla cream on top, and chill.

Separately, glaze the top pastry layer with fondant or egg white glaze, let dry, and place on top just before cutting.