Bring a small saucepan of water to the boil, add the lentils and cook over a medium heat for about 10 minutes until al dente, then drain and set aside.
Meanwhile, heat the sunflower oil in a large, heavy-based frying pan, add the garlic, ginger, onion, and green chili and cook over a medium heat, stirring occasionally, for 5-6 minutes until the onion is lightly golden. Stir in the chili powder, cumin, ground coriander, yogurt and garam masala and cook for a further 1-2 minutes.
Pour in the measured water and bring to the boil, Stir in the tamarind paste, curry powder, lentils, and chickpeas and return to the boil. Reduce the heat to medium and cook, uncovered, for 15-20 minutes or until the mixture is thickened.
Ladle the curry into warm bowls, drizzle with the extra whisked soya yogurt, and garnish with chopped coriander, sliced green chilis and hot chili powder. Serve with lemon wedges for squeezing over, if liked.