Easy vegetable curry

Name: Easy vegetable curry
Ingredients: 2 medium potatoes (around 350g/12oz), peeled and cut into 2cm/¾in chunks; 1 large carrot, peeled and sliced diagonally; ½ cauliflower (around 300g/10½oz), cut into small florets and halved; 3 tbsp sunflower or vegetable oil; 1 large onion, coarsely grated or very finely chopped; 1 tbsp medium or hot curry powder; 1 x 227g tin chopped tomatoes; 300ml/10fl oz vegetable or chicken stock (made with ½ cube), gluten-free if required; 100g/3½oz frozen peas or two large handfuls young spinach leaves, or a mixture; plain yoghurt or vegan alternative, to serve; mango chutney, to serve