Prepare by slicing up the aubergine into rounds and chopping the onion.
In a large frying pan, heat up a tablespoon of oil and fry a third of an aubergine at a time on both sides until it is soft and golden. Repeat this for the rest of the aubergine, adding another tablespoon of oil for each third. Transfer the aubergines to the slow cooker pot as they are done.
Once all the aubergine is fried, use the remaining oil to fry the onion.
After about 5 mins add crushed garlic, smoked paprika and cumin. Stir these in and cook for about a minute.
Add the lentils, tomatoes and some salt and pepper. Bring to the boil.
Add the mixture to the slow cooker pot along with the vegetable stock. Mix well.