Heat the olive oil in a pan over a medium to high heat, add the onion, bay leaf and a pinch of salt and cook, stirring, for about 10 mins, until the onion is softening and just starting to colour. Add the garlic and chilli and cook for a couple of mins more. Mix in the tomatoes and red wine vinegar, and cook, stirring, for about 10 mins until they are collapsing. Add the aubergine, and mix well with the other ingredients, cooking for a few more mins, then add the lentils and 100ml water. Continue to cook until most of the water has reduced. Season. Serve the warm ragu on top of a generous serving of swede purée. Garnish with the walnuts and parsley.