Keralan chicken coconut ishtu

Name: Keralan chicken coconut ishtu
Ingredients: 5 tbsp coconut oil or vegetable oil; 5cm/2in cinnamon stick; 6 green cardamom pods; 4 cloves; 10 black peppercorns lightly crushed; 1 star anise; 15 curry leaves; 1 medium onion finely sliced; thumb-sized piece of ginger peeled and finely chopped; 6 garlic cloves finely chopped; 2-3 green chillies; 2 tsp fennel seeds; ½ tsp ground turmeric; 1 tbsp ground coriander; 600g chicken thighs skinned; handful green beans ends trimmed, halved if very long; 400ml can coconut milk; 2 tbsp coconut cream; 1 tsp vinegar (or to taste); large handful baby spinach blanched and water squeezed out; small handful fresh coriander to garnish