Spiced parsnip shepherd's pies

Name: Spiced parsnip shepherd's pies
Cook time: 1 h
Total time: 1 h
Cuisine: British
Ingredients: 2 tbsp sunflower oil; 1 large onion , chopped; 2 garlic cloves , crushed; small knob of ginger , peeled and granted; 2 tbsp medium curry powder; 500g minced beef or lamb; 400g can chopped tomato; 100g frozen pea; 600g parsnip , peeled and chopped into large chunks; large potato , peeled and chopped into large chunks; 1 green chilli , deseeded and chopped; large bunch coriander , chopped; 2 tsp turmeric; juice of 1 lemon; 50g butter