For red curry paste, pound onion, garlic, coriander roots and galangal in a large mortar and pestle to a coarse paste, then transfer to a food processor. Pound remaining ingredients (except peppercorns) with 1 tbsp sea salt to a coarse paste, then add to processor and process to a smooth paste, stir through pepper. Makes 250ml.
For cucumber relish, combine vinegar, sugar, coriander root and garlic in a small saucepan, bring to the boil, remove from heat, strain and cool to room temperature. Combine cucumber, ginger, shallot, chilli and coriander leaves in a bowl, add vinegar mixture and set aside. Makes about 300ml.
Melt coconut oil in a large saucepan over low-medium heat, add curry paste and 1 tsp sea salt, stir until fragrant and roasted (10-15 minutes). add beef, cook until sealed (2-3 minutes). Add stock and coconut cream, cook until fragrant (2-3 minutes). Season to taste with fish sauce and palm sugar, cook over low heat until meat is tender (2½-3 hours), adding more stock if necessary. Add wild ginger, lime leaves, chilli and peppercorns and season to taste – it should be hot, salty and sweet. Add basil, simmer for 5 minutes, then serve scattered with kaffir lime and chilli, with steamed rice and cucumber relish to the side.