Prepare Spice Powder: In a frying pan, dry roast cinnamon sticks, long pepper, cubeb, green cardamom, black peppercorns, and cumin seeds on medium flame for 2-3 minutes until fragrant. Let cool, then crush to powder using mortar and pestle.
Mix Ground Spices: Add salt, coriander powder, red chilli powder, garam masala powder, and turmeric powder to the crushed spices and mix well. Set aside.
Prepare Kabab Mixture: In a chopper, combine beef, chopped onion, ginger garlic paste, chopped green chillies, hung yogurt, bread slices, the ground spice mix, mint leaves, fresh coriander, butter, and yellow food color (if using). Chop until well combined. Refrigerate the mixture for 15 minutes.
Shape and Cook Kababs: With wet hands, take about 130g of the mixture and skewer it on metal skewers. Heat a griddle, add cooking oil and butter, and fry kababs on low flame until golden brown, applying melted butter in between. This recipe makes about 7 kababs.
Toast Naan: On the same griddle, toast naan on both sides until warm and slightly crisp.
Prepare Sauce: In a bowl, whisk together green chutney, yogurt, cream, and salt until smooth.
Assemble and Serve: Place kababs on toasted naan, drizzle with prepared sauce, and sprinkle chaat masala to taste. In a small frying pan, melt butter and pour over kababs. Garnish with chopped fresh coriander and serve immediately.