01 - In a large bowl, whisk together yogurt, lemon juice, ginger-garlic paste, ground cumin, coriander, chili powder, garam masala, and salt until well combined. Add chicken pieces and toss to coat thoroughly. Cover bowl and refrigerate for at least 30 minutes, up to 2 hours for maximum flavor penetration.
02 - Melt 2 tablespoons butter in a large skillet over medium heat. Add finely chopped onion and sauté until golden brown, approximately 5 minutes. Add marinated chicken pieces, reserving any excess marinade in the bowl. Cook chicken until lightly browned on all sides, about 6 to 7 minutes.
03 - Pour crushed tomatoes into the skillet along with reserved marinade and sugar. Reduce heat to low and simmer for 10 minutes, stirring occasionally. Stir in heavy cream and remaining 1 tablespoon butter. Continue cooking for 5 to 7 minutes until sauce thickens nicely and chicken is completely cooked through. Season with additional salt if desired. Garnish with chopped fresh cilantro before serving.
04 - In a large mixing bowl, combine grated zucchini, grated carrot, diced red onion, thawed peas, corn kernels, eggs, all-purpose flour, chickpea flour, turmeric, cumin, chili powder, salt, black pepper, and baking powder. Mix thoroughly until a thick, cohesive batter forms.
05 - Pour approximately ½ inch of oil into a large skillet and heat over medium temperature. Drop heaping tablespoons of batter into hot pan, flattening slightly with back of spoon. Fry for 2 to 3 minutes per side until golden brown and crispy. Transfer fritters to paper towel-lined plate to drain excess oil.
06 - Serve butter chicken immediately hot from the stove, accompanied by freshly fried vegetable fritters on the side. For a complete meal, consider pairing with steamed basmati rice or warm naan bread.