Whisk yogurt, egg, ginger-garlic paste, salt, chili powder, coriander, cumin, and 1 tablespoon lemon juice in a medium bowl until thoroughly combined. Finely chop 6 of the curry leaves; stir into yogurt mixture. Stir in chicken until all pieces are coated with marinade. Cover and refrigerate for at least 30 minutes or up to 24 hours.

Pour oil into a large Dutch oven to a depth of at least 1 inch. Heat over medium-high to 335°F. Meanwhile, line a baking sheet with a wire rack, and set aside. Remove chicken from refrigerator; add cornstarch to chicken mixture, and stir until all chicken pieces are coated.

Once oil reaches 335°F, working in 2 batches, carefully add half of coated chicken pieces, a few at a time, to Dutch oven. Reduce heat to medium (maintaining a temperature around 315°F); cook, undisturbed, until coating adheres to chicken and is lightly browned, 1 to 2 minutes. Stir and turn chicken pieces; continue cooking, stirring often, until chicken is well browned and a thermometer inserted into thickest portion of chicken registers 165°F, 3 to 4 minutes. Transfer to the prepared baking sheet. Allow oil temperature to return to 335°F, if needed; repeat frying process with remaining chicken pieces.

Once all chicken is cooked, transfer 2 tablespoons hot frying oil to a large skillet over medium. Stir in garlic and remaining about 14 curry leaves; cook, stirring constantly, until garlic is fragrant and curry leaves are crisp, 1 to 2 minutes. Stir in fresno and serrano chiles and remaining 1 tablespoon lemon juice; cook, stirring often, until chiles are fragrant, about 30 seconds. Add cooked chicken; toss and stir until chicken is coated with curry leaf mixture and is warmed through, about 1 minute. Transfer to a plate, and season with additional salt to taste. Garnish with red onion slices and lemon wedges; serve hot. Recipe developed by Renu Dhar