Sift icing sugar, all-purpose flour, cornstarch, and fine salt into a mixing bowl. Rub in cold, diced unsalted butter until the mixture resembles coarse sand. Add the beaten egg and stir until the dough comes together. Form into a disc, wrap, and chill for 30 minutes.

Preheat oven to 160°C (320°F) fan. Roll out the dough to 3mm thickness and transfer it to a tart tin, trimming excess dough. Bake for 15-20 minutes until golden. Cool completely.

Lower oven temperature to 120°C (248°F). Combine eggs, granulated sugar, vanilla extract (or paste), and a pinch of salt in a bowl. Whisk until smooth. Gradually pour cream/milk, stirring for a silky consistency.

Pour custard over the cooled biscuit base. Bake for 45-55 minutes until edges set and center slightly wobbles. Cool to room temperature, then chill for at least 4 hours.

Melt granulated sugar in a saucepan over medium heat until it turns golden amber. Pour warm glaze over the custard and let cool before slicing.

Slice gently and optionally garnish with fresh fruits or whipped cream. Chill and enjoy the delightful flavors.