• Pour milk into a pan and add the butter. Heat it on low heat until butter melts and then take it off the heat.
• In a large bowl, whisk together the caster sugar, vanilla, whole egg and a yolk. Then add the sourdough starter, flour and a pinch of salt and whisk to combine.
• Pour the lukewarm milk mixture into the egg mixture. Whisk continuously until you get a smooth mix without any lumps. The batter will be quite thin, resembling a pancake mix.
• Cover with cling film and leave the mixture to rest overnight in the fridge.

DAY 2:

• When you're ready to bake, remove the canelés mixture from the fridge to bring it to room temperature and preheat your oven to 230°C Fan.
• Remove canelés mix from the fridge and give it a good stir before pouring into the moulds, but make sure to leave ½ cm from the top unfilled, as your pastries will rise a little.
• Bake in the oven at 230°C for 15 minutes only, then lower the temperature to 180°C for a further 40-45 mins.
• Remove from the oven when the tops or canelés are dark brown and crispy. Leave to cool down for at least 15 minutes before attempting to remove them from their moulds.