Heat oil or ghee in a large pan over medium heat. Add garlic and ginger paste, then methi, and cook for 30 seconds until fragrant.
Add onion paste and cook for 3-4 minutes until golden brown, stirring frequently.
Stir in mixed spice powder and garam masala, cooking for 1 minute. Add diluted tomato puree and cook for 2 minutes.
Add ketchup, mango chutney, lemon juice, sugar, and salt. Mix well and cook for 3-4 minutes.
Cook sauce until thickened, adding water gradually to achieve desired consistency.
Add chicken pieces, ensuring they're well coated with sauce. Simmer for 12-15 minutes until chicken is fully cooked.
Stir in mint, coriander, and cream. Cook for another 2-3 minutes.
Optional: add a few drops of red food coloring for authentic restaurant appearance.