Red cabbage salad

Name: Red cabbage salad
Ingredients: ½ red cabbage, cored and finely shredded; ¼ Savoy cabbage, cored and finely shredded; 1 large carrot, finely shredded; 1 red grapefruit, peeled and segmented; 2 tbsp finely chopped fresh mint leaves, plus extra to garnish; 2 tbsp finely chopped fresh coriander, plus extra to garnish; 4 tbsp natural yoghurt; 2 tbsp mayonnaise; 1 tsp cumin seeds, toasted; 2 limes, juice only; 1 tsp finely grated fresh root ginger; 1 red chilli, finely chopped; 2 tsp clear honey; sea salt; 1 tsp nigella seeds, to garnish