Accurately weigh out all the required ingredients according to the recipe. Place all the ingredients except the butter, orange zest and egg wash in a mixer. Mix on medium speed while adding the butter. Once it is mixed in, add the orange zest. Stop the mixer and, using a plastic scraper, scrape down the inside of the mixing bowl. Mix again for 10 to 15 minutes on medium speed until the butter is fully incorporated into the mixture. The dough will be shiny and elastic. Place the dough in a lightly oiled plastic container with a lid and ferment overnight in the refrigerator.
One hour before baking, place your terracotta baking stone in the oven and preheat the oven to 200 degrees Celsius. Place the dough on a floured work surface and divide into 450g balls for large brioches and 60g balls for small brioches. Round up, cover with a damp cloth and leave to rest for 10-15 minutes. Mould into one well-greased large brioche tin, or eight well-greased small brioche tins. Place in a warm area of your kitchen until the dough doubles in size. Brush the tops of the brioches with egg wash. Bake until golden brown: large brioches should take 25-30 minutes and small brioches 12-15 minutes. Remove from the oven, turn out of the tins and allow to cool.
Serve with a little homemade strawberry jam or dip into a steaming hot cup of café au lait.