- Flake the mackerel into small pieces and combine with the red cabbage and beetroot in a large bowl.
- Mix 2 tbsp of the sour cream with the horseradish sauce.
- Warm the tacos according to the packet instructions.
- To serve, spread a little of the horseradish and sour cream mixture inside the tacos and fill generously with the mackerel mixture. Top with the extra sour cream, coriander and a squeeze of lemon juice.