Heat the oven to 170C. Melt the butter and set aside to cool for a moment. In a large bowl combine the sugars and pour over the butter. Beat together until combined. Add the egg and yolk and continue to mix.
Fold in the flour and when combined fold in the raisins. Scoop 8 large dollops of mixture onto 2 non stick baking sheets, making sure you leave plenty of room for them to expand when they cook.
Bake for 15-17 mins until they are cooked at the edges but still soft in the middle. Allow to cool on the baking sheet then keep in an airtight tin.