To make the burnt vanilla, preheat the oven to 180 degrees celsius, gas mark 4.
Place the vanilla pod in the oven for 5 minutes or until it puffs up.
Leave to cool before blitzing into a fine powder in a blender or food processor.
Line a large baking sheet with baking paper.
Cream the butter and icing sugar until light and fluffy - approximately 8 minutes.
Beat in the burnt vanilla powder and vanilla extract. Add the flour and milk and mix to form a soft dough.
Shape tablespoons of the dough into crescent moon shapes and arrange on the baking sheet.
Bake in the preheated oven for 15 minutes or until turning golden.
Immediately dust in the icing sugar to coat while still warm.