1. Place all of the ingredients into a food processor and whizz until smooth. Give it a taste and adjust the seasoning accordingly.
2. Pop in the fridge until the pate has firmed up slightly. Add crusty bread and watercress to serve.The pate will keep for a few days in the fridge, making it a simple and tasty work lunch. Out of mackerel? This recipe also works superbly with smoked salmon, canned tuna or sardines.