Prepare a 22cm/8.6 inch tart tin

Place flour, sugar, salt, cornstarch and butter in the bowl and rub between your fingertips until the dough resembles sands

Add the egg and knead until a smooth dough

If too wet add a little more flour, if too dry add a splash of milk (or put all the ingredients in a food processor and blitz until it forms a dough)

Roll the tart dough out into a circle slightly larger than your tart tin

Line the tart tin with the pastry and trim the edges

Dock (poke) the base of the pastry with a fork and place in the fridge to chill for 1-2 hours

Preheat the oven to 180C

Place a piece of baking paper in the unbaked tart shell and fill it with baking beans

Blind bake the tart pastry for 30 minutes, then remove the baking beans and baking paper and bake for another 10-15 minutes, or until golden brown (if the edges are getting too dark, cover them with aluminium foil)

Combine the cream cheese, ricotta/mascarpone, parmesan, milk and butter in a large heatproof bowl

Melt the cheeses over a double boiler, mix until smooth

Add the eggs, vanilla, cornstarch and sugar, and continue stirring the mixture until thickened (at least 10 minutes)

Remove from heat and cover with cling wrap. Chill in the fridge for at least 1 hour until chilled.

Preheat the grill to 240C/465F

Fill the baked tart shell with the cream cheese filling and smooth off the top

Lightly brush the top with the beaten egg yolk

Bake the cheese tart for 10 minutes (at least), or until lightly golden (if still liquid, then bake longer at lower temperature)

Use a fine-meshed sieve to sprinkle over the icing sugar on top of the tart

Using a blow torch, torch the top of the tart until it is burnished

Place in the freezer to set for 1 hour

Remove, slice and bring to room temperature