Tip lentils into a medium saucepan. Cover with the water and add turmeric and bay leaf. Stir and bring to a boil, then reduce to a simmer and cook for 10-15 minutes until the water has reduced and the lentils are soft.
After roasting the eggplant, remove its skin and mash the flesh in a bowl, ensuring the garlic is mashed and mixed well. Set aside.
Heat some oil in a pan over a medium heat. Add the onion and allow it to caramelise, about 10 minutes. Add the cumin seeds and cook for a further 2-3 minutes until fragrant then add curry leaves and stir for 1 minute.
Tip the onion mix into the saucepan of red lentils and stir. Add mashed eggplant, salt and garam masala and cook for a further 10 minutes. Season further if required.
Serve with brown rice, fresh herbs and tamarind chutney.