Grapefruit chicken stew with couscous

Name: Grapefruit chicken stew with couscous
Ingredients: 1kg/2lb 4oz skinless boneless chicken thighs, diced; 1 tsp ground turmeric; 4 tbsp olive oil, plus a little extra; 3 garlic cloves, finely chopped; 1 small onion, finely chopped; 1 tsp salt; 2 tsp ground cumin; 1 tsp chilli flakes; ½ tsp ground turmeric; 1 large grapefruit, juice and zest; 500ml/18fl oz hot water; 2 tbsp cornflour mixed with 2 tbsp water; large handful fresh flatleaf parsley, finely chopped; 400g/14oz couscous; 2 tbsp unsalted butter; 550ml/1 pint boiling water