Heat the oven to 190°C, or 170°C fan.
Rub the butter into the flour and salt until the mixture resembles breadcrumbs.
Add the egg yolk and enough cold water to bring it together into a dough.
Wrap and chill for 30 minutes.
Roll the pastry out and use it to line a 20cm tart tin.
Prick the base, line with baking paper and baking beans, then blind bake for 15 minutes.
Remove the paper and beans and bake for another 5 minutes.
Reduce the oven to 175°C, or 155°C fan.
Trim the rind from the Brie and arrange the rind over the base of the pastry case.
Crush the saffron and mix it with 1 teaspoon of warm water.
Leave it to infuse for a few minutes.
Whip the soft Brie until creamy, then beat in the egg yolks.
Add the sugar, ginger, nutmeg, saffron and salt and continue mixing until smooth and light.
Spoon the whipped Brie mixture over the rind in the pastry case and smooth the top.
Bake for 25 to 30 minutes, until the filling is set around the edges with a slight wobble in the centre.
Leave to cool for at least 20 minutes before slicing.
