In a large bowl, cream together the butter, peanut butter, light brown soft sugar and caster sugar until smooth. Beat in the eggs one at a time, then stir in the golden syrup, water and vanilla. Combine the flour, bicarbonate of soda and salt; stir into the peanut butter mixture. Fold in the fudge chunks and white chocolate drops. Heap spoonfuls about 7cm apart onto ungreased baking trays.
Bake for 12 minutes in the preheated oven, or until edges are golden. Remove from the oven and allow cookies to cool for 1 minute on the baking tray before transferring to wire racks to cool completely.