Place the flour, salt, yeast and sugar in the bowl of a food mixer with the dough hook fitted.
Crack the eggs into a jug and mix with a fork, then pour this into the flour mixture and beat on a slow speed for 6-8 minutes until the dough starts to come away from the sides of the bowl.
Take the butter and cut it into cubes and slowly add it to the mixer beating on medium speed until all of the butter has been incorporated. Make sure the butter has been mixed in before adding the next lot.
Mix on medium-high for 5 minutes until the dough is elastic and pulled away from the sides.
Place a towel or some cling-film over the bowl and leave it to prove for two hours or until doubled in size.
Then knock back the dough by knocking the air out of it and giving it a light knead.
Cover the bowl again with Clingfilm and place in the fridge overnight to rest.
Next make the creme patissiere, put the milk, vanilla and butter in a saucepan and bring them to a boil.
In another bowl mix the egg yolks, sugar, corn flour and plain flour together until pale in colour.
Gently pour the hot milk into the egg mixture and stir the whole time to combine and make sure the eggs don't cook. Return the mixture to the saucepan and stir or whisk until the creme patissiere is thickened. Taste a tiny amount to make sure all of the flour has been cooked off.
Place in a bowl and cover with cling-film, pressing it on to the surface of the creme patissiere and place it in the fridge to cool.
Take the brioche from the fridge and roll it out on a lightly floured surface until it measures roughly 45 cm x 30 cm and is about 1-1.5cm thick.
Whisk the creme patissiere to loosen it and then spread it evenly over the brioche, leave a couple of cm gap along one long edge so that the creme patissiere doesn't spill out when you roll it up.
Sprinkle the chocolate chips evenly over the dough and then roll the dough up to form a large swiss roll, trim the ends. You can still use these, but not as part of the finished bread. You should be able to cut the dough into 9 strips after it has been trimmed.
Grease the 23cm tin and place one brioche in the middle and arrange the other 8 around the edge, you may need to squeeze them in a little.
Cover the brioche lightly with cling-film and allow it to prove until doubled in size, probably about 3 hours as the dough will be cold from the fridge.
Then preheat the oven to 180C/160C Fan/Gas Mark and glaze with beaten egg yolk mixed with a few drops of warm water, bake for 35 mins, or until golden and crunchy to the touch.