Prepare the ground spices for the paste by stirring 9 g ground coriander, 10.4 g chilli powder, and 3 g ground turmeric with 4 tablespoons of water in a small dish.
Warm 3 tablespoon oil in a wide, heavy pan set over medium heat. Tip in 300 g chopped onion and cook for 2 minutes until translucent, then introduce 12 g chopped ginger and 24 g chopped green chilli, frying for 2 to 3 minutes more until the onions turn pale gold.
Add the ginger and garlic pastes (13 g ginger paste and 13 g garlic paste) and cook for 1 to 2 minutes until their moisture evaporates. Pour in the ground spices for the paste and sauté for another 2 to 3 minutes until the liquid cooks off.
Tumble in 400 g chopped tomato and 45 g kokum, pour in 500 ml water, and season with salt to taste. Bring to a rolling boil, then drop the flame to low and let it simmer for roughly 5 minutes until reduced by half.
Slide in 16 prawns and return the liquid to a boil. Lower the heat, scatter over 5–6.2 g curry leaf, and simmer gently for 3 to 4 minutes.
Lift the pan off the heat, stir in 127 g coconut milk, then return to a low flame to simmer for 2 to 3 minutes longer. Take off the heat and adjust the salt if needed.
Use 50% of the weight and stir in near the end of cooking. Adds warmth and depth since it contains ground coriander, but introduces stronger spices like clove and cinnamon.
Steep a tiny pinch (0.1 g per 2 g turmeric) in 2 tbsp warm water; use to match the rich golden hue. Contributes an aristocratic, honeyed floral flavour rather than earthy bitterness.
Use 80% of the weight, finely shredded and browned slowly with a pinch of asafoetida. Replicates the bulk and natural sweetness in gravies without allium.
Use 40% to 50% of the fresh tomato weight mixed with a splash of water. Imparts a deeper red colour, thicker sauce, and slightly sweeter cooked flavour.
Use equal weight; simmer gently over low heat to prevent curdling. Imparts a comparable rich texture, though it adds dairy richness without any coconut fragrance.