Prepare the Mutton Mixture: In a large mixing bowl, combine minced mutton, onion, ginger-garlic paste, green chilies, coriander, mint, cumin powder, coriander powder, garam masala, chili powder, salt, gram flour, and lemon juice. Mix well until all ingredients are well combined. Add the egg if using, and knead for a few minutes to help the mixture bind.
Marinate: Cover the bowl with plastic wrap and refrigerate for at least 2 hours (overnight is even better). This allows the spices to penetrate and tenderize the meat.
Shape the Kebabs: Take small portions of the mixture and shape them into bite-sized oval or round kebabs. If using skewers, gently press each kebab onto the skewer.
Cook the Kebabs: Grilling Method: Preheat grill or tandoor. Brush with a little oil and cook the kebabs on medium heat, turning occasionally, until evenly browned and cooked through (about 10–12 minutes).
Pan-Frying Method: Heat oil in a non-stick pan. Cook kebabs on medium flame for 3–4 minutes per side until crisp and golden.
Serve Hot: Arrange the kebabs on a platter, garnish with onion slices, and serve with lemon wedges and mint chutney.