1 For the turkey and vinegar sauce, blitz all the ingredients except the turkey in a blender until completely smooth. Pass through a fine sieve to remove any fibrous ginger bits. Cut the turkey into chunks or strips about 2cm thick and marinate for 12-24 hours in the liquid. Drain the marinade into a saucepan and boil for a few minutes. Pass through a fine sieve again and keep in the fridge until needed.
2 For the tartar sauce, cut half of the gherkins into fine dice. Add all remaining ingredients to a blender and purée until smooth. Stir in the gherkins.
3 For the batter, heat your oil to 180°C. Mix together all the other ingredients. Pat the surface of the turkey with kitchen towel to ensure that it’s quite dry, then coat in batter and fry in batches at 180°C for 6-8 minutes, until a rich golden brown. Drain on kitchen towel.
4 To serve, place the turkey on a bed of shredded cabbage and top with the tartar sauce. Serve the vinegar sauce on the side in a small pot or ramekin.
5 For the baked sweet potato with yuzu butter cut the butter into small chunks and beat in the yuzu juice and soy sauce until completely homogenised and no droplets of liquid remain (you may want to use an electric mixer for this). Pack into a container and chill until set.
6 Heat the oven to 180°C, gas mark 4. Scrub the sweet potatoes and cut off any eyes or gnarly bits. Cook them for 45 minutes to 1 hour, depending on their thickness – they’re done when you can go all the way through them with a chopstick. Leave them to cool slightly before eating.
7 Cut the butter into chunks (about 15g per potato). Split open the sweet potatoes and stick the butter inside. Garnish with a sprinkle of sesame seeds. Serve with the turkey and tartar sauce.