Order of addition
The sequence in which spices enter the pan, set by how fast each burns and how fragile its aroma is.
Also: spice timing, when to add spices, sequence of spices
Order of addition is a practical rule. Hard whole spices such as bay leaf, cinnamon, cardamom and cloves go in first, since they need time and fat. Seeds such as mustard and cumin follow, then aromatics like onion and ginger. Ground spices go in later, with a splash of liquid close behind, because their fine particles scorch within seconds. Tomatoes or other liquids stop the frying. Finishing spices such as garam masala, fresh herbs and citrus go in last. Chillies and turmeric are especially prone to turning bitter in dry heat. Many recipes fail because spices are added together, rather than in sequence.