Curried lentil pies

Ingredients

• 2 tablespoons ghee (clarified butter)
• 1 medium_piece (150g) brown onion, chopped finely
• 2 cloves garlic, crushed
• 4 centimetre (1½-inch) piece (20g) fresh ginger, grated
• 1 fresh long red chilli, chopped finely
• 1 large_piece (20g) carrot, chopped coarsely
• 1 (150g) stalk celery, trimmed, chopped coarsely
• 2 teaspoons black mustard seeds
• 2 teaspoons ground cumin
• 2 teaspoons ground coriander
• 1 teaspoon ground turmeric
• 1 1/2 cup (300g) brown lentils
• 410 grams (13 ounces) canned crushed tomatoes
• 2 cups vegetable stock
• 2/3 cup (160ml) coconut milk
• 1/2 cup (60g) frozen peas
• 1/2 cup fresh coriander (cilantro) coarsely chopped
• 600 grams (1¼ pounds) pumpkin, chopped coarsely
• 2 medium_piece (400g) potatoes, chopped coarsely
• 60 grams butter