Spinach, sweet potato & lentil dhal

Name: Spinach, sweet potato & lentil dhal
Prep time: 10 min
Cook time: 35 min
Total time: 45 min
Cuisine: Indian, Asian
Ingredients: 1 tbsp sesame oil; 1 red onion, finely chopped; 1 garlic clove, crushed; thumb-sized piece ginger, peeled and finely chopped; 1 red chilli, finely chopped; 1 ½ tsp ground turmeric; 1 ½ tsp ground cumin; 2 sweet potatoes (about 400g/14oz), cut into even chunks; 250g red split lentils; 600ml vegetable stock; 80g bag of spinach; 4 spring onions, sliced on the diagonal, to serve; ½ small pack of Thai basil, leaves torn, to serve