Preheat the oven to gas 5, 190°C, fan 170°C and line two large baking trays with baking paper.
Put the caster sugar and fresh lavender into a food processor and blitz the two together for 2-3 minutes to allow the lavender to scent the sugar.
Put the butter in a large mixing bowl and beat with a wooden spoon until smooth. Add the lavender sugar and beat again until fluffy and light.
Stir in the egg, then in a small dish milk the lavender food colouring with the milk and add this to the sugar, butter and egg mixture.
Add the flour and baking powder and gradually combine to form a soft dough. Stir in the white chocolate chips.
Shape the dough into a ball and wrap it in cling film and leave to chill in the fridge for 30 minutes.
Split the dough into 16 pieces, then roll into a ball and space them out on the trays so they have room to spread a little.
Bake for 16-18 minutes, until lightly golden. Leave to cool for a few minutes, before moving onto a wire rack to cool.