Cut a criss-cross in the aubergines, keeping the aubergines whole at the stem.
Put a large pinch of salt in a small bowl, add 2 tablespoons water and stir until dissolved.
Heat the oil in a kadhai or deep, heavy-based pan over high heat. Reduce the heat, add the fenugreek seeds, mustard seeds, and kalonji seeds, and stir-fry for 1 minute, or until all the seeds start to splutter. Add the ground spices together with the salt mixture and stir-fry for 30 seconds. Remove the pan from the heat.
Fill the aubergines with equal quantities of the mixture, then place the aubergines back in the pan, cover and cook over very low heat for 5-7 minutes, turning gently once or twice, until hot.