In a large bowl, mix together the flour, bicarbonate of soda and salt. Add the buttermilk, skimmed milk and egg then stir together well, taking care not to over beat. Leave the batter mixture to stand for 10 minutes.
Break the Boursin cheese into small lumps and stir through the batter mixture.
Melt a little of the butter in a frying pan until hot and cooking the cakes in batches, drop tablespoons of the batter mixture into the pan well spaced apart. Cook for about 3 minutes on a medium heat, then flip over and cook for a further 3 minutes.
Transfer to a warm plate, keep warm and repeat with remaining butter and batter.