Warm a pan to medium heat, then roast the cumin and mustard seeds without fat for about 30 seconds until the seeds start to smell and pop. Put on a plate and let cool down. Heat the sunflower oil in the pan, stew the diced potatoes for 3-4 minutes until they start to soften. Add onions, garlic, chili powder and turmeric and simmer everything briefly. Then add the aubergine cubes with the roasted spices, the poppy seeds, the broth and a little salt, cover and simmer for 30-45 minutes. Season the curry to taste and serve sprinkled with coriander greens.