Dry-roast dried prawns over gentle heat until fragrant. Cool, then grind to a fine powder.
Heat oil in a large saucepan, then sauté mustard seeds and curry leaves briefly over moderate heat until seeds start to pop. Stir in onion, garlic, ginger, chilli and minced turmeric, then cook for 1-2 minutes to soften. Add coconut cream and fenugreek seeds and cook, unc