Preheat the slow cooker if necessary; see the manufacturer's instructions. Heat the oil in a frying pan, add the onion and fry, stirring, for 5 minutes or until softened and just beginning to turn golden.
Stir in the spices, dried chillies, sweet potatoes and garlic and fry for 2 minutes. Add the tomatoes, lentils, stock and sugar and season with a little salt and pepper. Bring to the boil, stirring. Spoon into the slow cooker pot, cover with the lid and cook on low for 6–8 hours.
When almost ready to serve, put the eggs in a small saucepan, cover with cold water and bring to the boil, then simmer for 8 minutes. Drain, crack the shells and cool under cold running water. Peel and halve, then add to the slow cooker pot with the peas, cream and half the coriander. Cover and cook on low for 15 minutes.
Spoon into bowls, garnish with the remaining coriander and serve with rice or warmed naan bread, if liked.