Start by combining the milk and 125g sugar in a saucepan. If using vanilla bean, add it to the milk at this point. Bring to the boiling point over low to medium flame.

In the meantime, mix the egg yolks, eggs and the remaining sugar in a bowl until pale and double in volume.

Stir in the flour, cornstarch and salt and mix well then pour in the hot milk, mixing while doing so to prevent the eggs from curdling.

Pour the mixture back into the saucepan and place back over heat.

Cook, whisking all the time, until the mixture becomes to thicken. Ideally, you should cook the pastry cream for 1-2 minutes to make sure the flour is cooked through. The cream will go through various stages of stiffness. At first, it will set quickly, then it will soften as you boil it and set again. To test if it's ready, dip the tip of a cold knife into the cream then allow it to cool down. If you can remove the cream off the knife without leaving traces of cream on the blade of the knife, the cream is ready.

Remove from heat and cover the cream with plastic wrap on its surface.

Allow to cool down completely before adding the vanilla extract.