Curried vegetable and chicken pie

2 tbsp sunflower oil

271g chicken fillets, chopped into chunks

1 onion, finely chopped

2 garlic cloves, chopped

1 green chilli, deseeded and finely chopped

1 tbsp garam masala

1 tsp ground turmeric and ground cumin

2 carrots, cubed

1 parsnip, cubed

225g cauliflower florets

1 courgette, cubed

75g frozen peas

25g butter

25g plain flour

4 tbsp Greek-style yoghurt

3 tbsp chopped fresh coriander

1 sheet shortcrust pastry

1 tbsp milk, to glaze