For the polenta, line two square casseroles (should have a total size of approx. baking tray) with baking paper. Bring milk, 300 ml water, vegetable stock and 1 tsp. salt to the boil. Take the pot from the stove, pour in 250 g polenta while stirring. Pour the mixture into the moulds and press flat to approx. 1⁄2 cm. Let it cool down and then let it cool down in the refrigerator for about 20 minutes.
Preheat the oven for the vegetables (electric cooker: 200 °C/circulating air: 180 °C/gas: see manufacturer). Clean and wash the cauliflower and divide into florets. Wash and halve the tomatoes. Peel and slice the onions. Peel and chop garlic. Clean, wash and roughly dice the aubergines. Mix everything on a baking tray. Sprinkle with 4 tablespoons of olive oil and season vigorously with salt and 1⁄2 tsp. chili. Bake in a hot oven for 25-30 minutes.
Mix yoghurt, tahini and half lemon juice, season with salt and pepper. Wash parsley, shake dry and puree with half of the yoghurt dip. Clean and wash spring onions, cut into rings.
Cut polenta into strips of about 1 cm wide and 7-8 cm long, sprinkle with some polenta. Heat the oil in a large frying pan and fry the polenta chips in it in portions for about 6 minutes until crispy all around. Drain on kitchen paper. Rinse and drain the lentils and fry them in 1 tbsp. olive oil. Mix with vegetables and the rest of the lemon juice. Arrange in bowls, sprinkle with spring onions. Serve with chips and yoghurt dip.