This dish is a great idea if you need to prepare something in advance, to be baked the next day. It is plenty enough for 6 adults to share and tastes the best when served with a side salad.
Saute the onion and garlic in coconut oil. Add chopped carrots and aubergines and cook for about 20 minutes. After that time add rinsed lentils, passata, thyme and some salt to taste. Cover and cook on a little heat for about 30 minutes. In the meantime cook potatoes with celeriac in salty water, drain and mash with coconut oil. Once the sauce is ready, put it into a baking dish and cover with mash. At that point you can either put it straight into the oven (180C) for about 20 minutes, or you can wait until it cools down, refrigerate and only bake it the next day or even later when needed.