Saag aloo

Name: Saag aloo
Prep time: 5 min
Cook time: 25 min
Total time: 30 min
Cuisine: Asian, Indian
Ingredients: 1kg Maris Piper potatoes, peeled and cut into 3cm pieces; 2 tbsp vegetable oil; 2 tsp cumin seeds; 2 tsp mustard seeds; 1 onion, finely sliced; 3 large garlic cloves, crushed; 3cm piece ginger, finely chopped; 1 tbsp tomato purée; 1 tsp ground coriander; 1 tsp hot chilli powder; ½ tsp turmeric; 250g bag spinach; 1 red chilli, finely chopped (optional)