Parisian custard tart

Rinse the pan with cold water to help keep the milk from scorching.

Heat the milk, water and half the sugar until really hot, watching that it does not boil over.

Whisk the rest of the sugar with the brown sugar, breaking up any lumps, and the cornstarch; whisk in the eggs, stirring as soon as they go in.

Whisk a couple of ladles of the hot milk into the egg mixture slowly to warm it, then pour in the rest in a steady stream, whisking.

Return to the pot and cook over a fair amount of heat, whisking constantly into the corners, until the custard thickens, the whisk leaves tracks and a bubble pops at the surface; keep stirring about a minute more.

Flavour the custard with vanilla and rum.

Cover and set aside at room temperature to cool.

Roll the puff pastry to about a 13 inch round and fit it into a buttered springform, easing it into the corners; pleats are fine. Trim the dough about an inch and a half up the sides.

Whisk the cold, firm custard smooth and pour it into the crust.

Set on a parchment-lined sheet and bake in a hot oven for 50 to about 55 minutes, until very dark on top.

Chill the tart; run a knife around the edge and warm the springform with a hairdryer if the cold butter sticks, then release.

Cut into large wedges; serve cold or at room temperature.