Place the blackberries in a bowl with the crème de mur and two tsps of caster sugar. Macerate while you infuse the milk. Place the milk, half the caster sugar and bay in a pan over a medium heat and bring to the boil, stirring until the sugar has dissolved. Boil for about two minutes, stirring, and then turn the heat off and leave to infuse for at least an hour. Remove the bay leaves
Preheat the oven to 180C and grease a baking dish just wide enough to hold the blackberries in one layer. Scatter over the demerara sugar and rotate to distribute the sugar evenly across the dish
Sift the flour into a bowl with the salt and sugar. Add in the eggs, beating until smooth, then mix in the melted butter. Gradually add the milk, whisking until you have no lumps, straining through a sieve if you’re not happy there are no lumps. Put the blackberries in the dish and gently pour over the batter. Bake for 30 minutes, until golden and just set but still wobbly. Leave to settle for 10-15 minutes then serve, warm.