Submerge 250 g new potatoes in cold water for 10 minutes to remove any soil. Drain, rinse well, and cut each into 4 to 6 slices.
Set a medium saucepan over medium-high heat and add 114 g vegetable oil or ghee along with 720 g puréed tomatoes. Stir in the ground spices for the sauce, 11.6 g salt, and 1 tablespoon crushed chilli flakes, cooking for 5 to 8 minutes until oil glistens on the surface.
Add 1 litre of water and bring the pan to a boil. Reduce the heat to medium and simmer for 12 to 14 minutes, stirring occasionally, until the sauce is smoothly emulsified.
Carefully add the sliced potatoes, cover with a lid, and maintain a steady boil for 5 to 8 minutes.
Take off the lid and stir in 250 g green beans (strings removed and halved lengthways). Cook uncovered for 5 minutes more until the vegetables are tender, then serve hot.
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 the same weight. Crush whole dried red chillies in a mortar, shaking out some seeds if you want less heat. Gives the same heat but a coarser, more uneven texture.
Use the same weight. Soak in hot water for 10 minutes if the recipe needs a paste, or crush dry for a flake-like texture. Slightly more work and less uniform.
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.