For the chicken: Set the garlic and ginger on a broiler rack and place under a hot broiler until charred on all sides. Leave to cool, then peel and roughly chop before putting into a mortar and pestle. Toast the coriander seeds and star anise in a dry frying pan over medium heat until aromatic; tip into the mortar and pestle and add the chile, lime zest and cilantro. Bash to a paste, then mix in the lime juice and fish sauce.
Smear the paste all over the flesh side of the chicken thighs. Arrange the thighs on a plate, cover with plastic wrap, and chill for at least 4 hours or preferably overnight.
To cook the chicken, heat a large heavy-based frying pan over medium heat. Add the sunflower oil and then the chicken thighs, skin-side down. Reduce the heat to very low and cook until the skin is nice and crispy, 20 to 30 minutes. (Don't shake the pan or touch the thighs during cooking; just leave them alone and you will produce the most fantastic crisp skin and succulent flesh.)
When you can see that the chicken thighs are nicely browned and the flesh is almost but not quite cooked through, turn the thighs over and cook for another 5 to 6 minutes, until completely cooked through and tender. Transfer to a carving board and leave to rest for 5 to 10 minutes.
For the dressing: Meanwhile, mix together the fish sauce, sugar, chile, lime zest and juice in a small bowl. Set aside until needed.
For the salad: Put the cabbage, bean sprouts, carrots, cilantro and mint in a large bowl; toss lightly to combine. Add dressing and toss to coat.
To serve, divide the dressed salad among 4 plates and then quickly carve the chicken into slices and pile on top. Scatter over the peanuts.