Preheat your oven to 160°C (320°F). In a mixing bowl, sift together the icing sugar, all-purpose flour, cornstarch, and fine salt.

Rub in the cold, diced unsalted butter until the mixture resembles coarse sand. Incorporate the beaten egg, mixing until just combined.

Shape the dough into a disc, wrap it in plastic wrap, and chill for 30 minutes.

Roll out the dough to about 5mm thickness and transfer it to a tart tin, pressing it into the edges. Prick the base with a fork.

Bake for 15–20 minutes, or until golden brown. Allow to cool completely.

Reduce the oven temperature to 120°C (250°F). Whisk together the heavy cream, milk, granulated sugar, vanilla extract, and extra cornstarch until well combined.

Pour the custard mixture into the cooled biscuit base and bake for about 45–60 minutes, or until the custard is set but wobbly in the center.

In a saucepan, combine granulated sugar and water to make the caramel glaze.

Boil without stirring until amber color is achieved. Add salt and let cool slightly before drizzling over the custard.

Chill the tart in the refrigerator for at least 2 hours before serving.