01 - Whisk together yogurt, lemon juice, ginger-garlic paste, cumin, coriander, chili powder, garam masala, and salt in a large bowl. Add chicken pieces and toss to coat evenly. Cover and refrigerate for at least 30 minutes or up to 2 hours for maximum flavor absorption.
02 - Melt 2 tablespoons butter in a large skillet over medium heat. Add chopped onions and sauté until golden brown and fragrant, approximately 5 minutes. Stir occasionally to prevent burning.
03 - Add marinated chicken pieces to the skillet, reserving any excess marinade. Cook until lightly browned on all sides, about 6-7 minutes. The chicken should develop a nice sear while remaining partially undercooked.
04 - Pour in crushed tomatoes, reserved marinade, and sugar. Reduce heat to low and simmer for 10 minutes, allowing flavors to meld. Stir in heavy cream and remaining 1 tablespoon butter. Continue cooking for 5-7 minutes until sauce thickens and chicken is fully cooked through. Adjust seasoning as needed.
05 - Combine grated zucchini, carrot, diced onion, peas, corn, eggs, all-purpose flour, chickpea flour, turmeric, cumin, chili powder, salt, pepper, and baking powder in a large bowl. Mix thoroughly until a thick, cohesive batter forms.
06 - Heat approximately ½ inch of oil in a large skillet over medium heat. Drop heaping tablespoons of batter into the pan, flattening slightly with the back of a spoon. Fry for 2-3 minutes per side until golden brown and crispy. Transfer to paper towels to drain excess oil.
07 - Spoon hot butter chicken onto plates and garnish with chopped fresh cilantro. Arrange vegetable fritters alongside. Serve immediately while fritters remain crisp.