Place the minced lamb, garam masala, ginger garlic paste and chopped coriander in a large bowl. Finely chop the tomato and the onion and add them to the minced meat. Now mix them all up together, season with salt to taste, then make long, sausage-like, rolls out of this mixture. Cook in a preheated moderate oven (Mk 3 - 325ºF - 170ºC) for 12 to 15 minutes, or grill over a barbeque for 6-8 minutes, turning frequently.