Soft Brioche

Whisk flour with cornstarch, salt and baking powder.
Add the melted butter. milk, oil, egg and sugar into the flour mixture. Knead until you get a smooth dough.
Reserve the dough for 1 hour.
Cut the dough into pieces and roll them into balls. Flatten each ball into a disc and cover half with melted butter and sesame seeds.
Roll out the discs of dough, overlapping them and leave to rise for 1 hour.
Brush with egg yolk and bake at 180°C/350°F for 25 minutes.