Butter a heavy ovenproof saucepan with a tight-fitting lid. Divide rice in three. Place a layer of rice on base. Scatter over half of mint, coriander and garam masala and half of onions. Repeat layers ending with rice. Pour over lemon juice. Stir together saffron and milk in a bowl. Pour over rice. Cover with a circle of parchment paper and the lid.
06Place in oven and steam for 30 to 40 minutes or until rice is tender.