The day before, prepare the brioche dough. Place the flour, salt, caster sugar, baking powder and eggs in the bowl of a food processor. Blend for about 5 min.
Add the soft butter and lemon zest. Blend again for 5 min.
Cover with a cloth and refrigerate overnight.
The next day, roll out the dough to a thickness of 1.5 cm and a diameter of 20 cm. Place in a mould.
Cover with a cloth and leave to rise at room temperature for 2 hours.
Prepare the crème pâtissière. Bring the milk to the boil with the vanilla pod, split in 2.
Preheat oven to 180°C (gas mark 6).
In a bowl, whisk together the egg yolks and powdered sugar.
Add the flour, then pour the boiling milk over it, stirring with a whisk and mixing well. Add 2 tablespoons orange blossom and stir.
Return to the pan and cook for 3 minutes, stirring as soon as the mixture returns to the boil.
Once the cream is cooked and thickened, pour onto a baking sheet, cover with cling film (to retain moisture) and cool quickly.
When the brioche has risen after 2 hours, brush with an egg yolk diluted in a little water and sprinkle with granulated sugar. Bake in a preheated oven at 180°C for approx. 30 min.
Once the brioche is cooked, remove from the oven and leave to cool, then cut into 2 thick slices.
Prepare the whipped cream. Place the food processor bowl, whisk attachment and crème fraîche in the freezer for 5 minutes.
Whip the cream at medium speed, adding the powdered sugar halfway through. Increase the speed until the cream is firm. Set aside in a cool place.
When the custard has cooled, mix with the whipped cream.
Using a piping bag, pipe the cream onto the brioche disk, close with the other disk, sprinkle with powdered sugar and chill until ready to serve.
