Frying the Masala Until the Oil Separates

In a tomato-based masala like the aloo dum, the cue to move on is the oil, not the clock. As the blended tomato, garlic and ground spices cook over medium heat, the mixture first loosens and bubbles, then darkens and thickens until beads of oil pool at the edges and rise to the surface. That separation — sometimes called bhuno or bhunnu — means the raw, sharp notes of the tomato and spices have cooked out and the base has concentrated into a glossy, deeply savoury masala. Stir frequently so it catches evenly without burning, and only fold in the parboiled potatoes once the oil has broken free; added too early, the sauce stays thin and tastes raw. This is the step Grace Dent singled out when she described how the nigella, tomato and garlic mellow really well together.