Prepare a tandoor or charcoal grill for moderate heat, or alternatively preheat the grill (broiler) to medium.
Put the meat, ginger, and garlic pastes, 2 tablespoons each of the chopped onion, spring onion, tomato, and pepper into a bowl. Add all the remaining ingredients, except the butter, and season with salt.
With damp hands, mix well, then divide the mixture into 16 equal portions and roll into balls. Spread the balls evenly along the length of metal skewers, flattening the mixture into sausage shapes until the kebabs are 10-cm / 4-inches long and leaving 2.5 cm / 1 inch between each one.
You can make 2 kebabs on one long skewer. Spread the remaining chopped vegetables evenly over each skewer.
Roast in a moderately hot tandoor, over a charcoal grill, or under the hot grill for 5-6 minutes.
Remove the skewers from the heat and hang them up over a tray for about 2-3 minutes to allow any excess moisture to drain out completely.
Put the skewers in a dish, baste with melted butter, and roast again in the tandoor, on the charcoal grill, or under the grill for a further 2-3 minutes.