Make The Dough
Tip the flours into the bowl of a stand mixer. Tip the sugar and yeast into the bowl on one side, and the salt onto the other side.
Zest in the lemon, scrape in the seeds from the vanilla pod and begin to mix with a dough hook.
Add the eggs and the milk, whilst kneading gently, and continue to knead until the dough comes together.
Add the softened butter, a little at a time, allowing it to incorporate (it will remain sticky).