Doughnuts filled with custard cream and Venetian mostarda

For the brioche dough, combine all the ingredients except the salt and butter pomade that we will put at the end, and mix until you get a smooth and elastic dough. Place in a bowl, cover, and keep in the fridge for 12 hours. Once this time has passed, shape the dough into balls of around 50g and let them rise at room temperature before frying on a medium heat.
For the custard cream, start by boiling half of the milk in a stainless steel pan. Then mix together the sugar, starch and flour, the remaining cold milk, egg yolks, lemon zest and vanilla and add them to the boiling milk.
Mix well and cook gently, leave to cool on a shelf and then fill the doughnuts with the mixture.
Garnish with the Venetian mostarda and icing sugar.