1.Place ancho chilli in a small heatproof bowl, cover with boiling water and set aside to soften (15 minutes). Drain water, reserving ¼ cup. Place chilli, reserved water, garlic, 1 tsp coriander seeds, paprika, 115gm honey and 1 tbsp vinegar in a small blender and blend until smooth; season to taste.
2.Place chicken in a large bowl. Add 2 tbsp honey marinade, season to taste and toss to coat; marinate (10 minutes).
3.For pickled watermelon, combine 1 tbsp sea salt flakes, remaining vinegar, coriander seeds and honey with 80ml water in a small saucepan over medium heat. Bring to a simmer, stirring to dissolve honey (2 minutes). Place watermelon and onion in a heatproof bowl. Pour over pickling liquid; refrigerate until cold.
4.Preheat a lightly greased barbecue or char-grill pan over medium heat. Thread chicken onto 10-12 metal skewers. Lightly brush with oil. Cook, basting frequently with remaining marinade, turning frequently, until charred and cooked through (10-12 minutes).
5.Serve skewers brushed with extra honey and serve with pickled watermelon scattered with micro coriander.
Ancho chillies are available from spice shops, specialty food shops and Mexican food stores.