In a mixing bowl, combine flour and salt. Add oil and rub into the flour with your fingers until crumbly. Gradually add water, kneading until a firm dough forms. Cover and let rest for 25 minutes.

Heat 2 tablespoons of vegetable oil in a skillet over medium heat. Add finely chopped onions and cook until soft and golden.

Add minced garlic, ginger, and optional green chili to the skillet. Sauté for 1 minute.

Add the ground chicken to the skillet. Cook, breaking up lumps, until no longer pink.

Stir in the spices: ground cumin, ground coriander, turmeric powder, garam masala, red chili powder, salt, and black pepper. Cook for 4-5 minutes, stirring until fragrant and chicken is fully cooked.

Mix in chopped cilantro and lime juice. Allow the filling to cool to room temperature.

Divide the rested dough into 6 equal balls. Roll each ball into a thin oval, about 6 inches long. Cut each oval in half to form 12 semicircles.

Shape each semicircle into a cone, sealing along the edge with a little water. Fill with 2 tablespoons of the cooled chicken mixture. Seal the top by pinching the dough together, forming a triangle.

Heat vegetable oil in a deep fryer or heavy pan to 170°C (340°F). Fry the samosas in batches for 4-5 minutes, turning until golden and crispy.

Drain the fried samosas on paper towels before serving.