Split the vanilla bean and scrape its seeds into a saucepan with 175 ml heavy cream and 175 ml milk.

Warm the vanilla cream mixture until steaming, then remove it from the heat and infuse for 60 minutes.

Whisk the 4 egg yolks with 40 g granulated sugar in a mixing bowl until pale.

Reheat the infused cream mixture until steaming, then slowly whisk it into the egg yolk mixture.

Return the custard to a clean saucepan and cook gently, stirring with a spatula until thickened.

Strain the custard through a fine sieve, then cover its surface and chill until cold.

Melt the white chocolate into the chilled custard, then churn the mixture in an ice cream maker until frozen.

Mix the remaining 110 g granulated sugar with ground cinnamon in a bowl, then melt 45 g butter.

Roll the cinnamon roll dough in the cinnamon sugar, then arrange the rolls in a buttered baking dish.

Pour 120 ml milk around the cinnamon rolls, then bake at 180°C / 350°F until deeply golden and caramelized.

Toast the walnuts in a dry saucepan, then remove them and roughly chop them.

Melt brown sugar with the remaining 25 g butter in a saucepan, then stir until a dark caramel forms.

Stir dark rum and toasted walnuts into the caramel, then simmer briefly until glossy.

Place warm cinnamon rolls on two plates and spoon rum walnut caramel over each portion.

Add a scoop of vanilla custard ice cream to each plate, then drizzle with remaining vanilla custard sauce.