The most critical spice in Kadai masala is dried red chili, as it provides the signature heat and vibrant color essential to the dish.
While all spices in Kadai masala contribute to its unique flavor profile, dried red chilies are arguably the most critical. They provide the foundational heat that defines Kadai Paneer. The type of chili used can vary based on preference, from milder Kashmiri chilies for color and subtle heat to hotter varieties like Byadgi or Guntur chilies for a more intense spice level. The chilies are typically dry roasted before grinding to enhance their flavor and aroma. Without the characteristic heat from the chilies, the Kadai masala would lack its signature kick and the dish would be significantly different. Other important spices like coriander seeds, cumin seeds, and peppercorns contribute depth and complexity, but the red chili is the backbone of the blend.
To control the heat level, remove the seeds from the dried red chilies before roasting and grinding. This allows you to enjoy the flavor and color without excessive spiciness.