Heat oil in a frying pan over medium-high heat. Add onions. Sauté, stirring occasionally, for 2-3 minutes or until the onions are soft and translucent. Add garlic, ginger, ground cumin, garam masala and red chili powder. Sauté, stirring, for 2 minutes or until fragrant. Add butter and tomato paste. Sauté, stirring, for 1 minute. Add cream, milk and yogurt. Stir to combine. Bring to a boil. Simmer 3-4 minutes or until the sauce is really thick. Set aside.

Place minced chicken, 2 tablespoon butter chicken sauce, garam masala and coriander (cilantro) leaves in a bowl. Season with salt and pepper. Mix. Divide the mince into four equal parts. Roll out balls and flatten them to make patties.

Meanwhile, heat oil in a frying pan over medium-high heat. Add the patties (in batches if needed). When one side is brown, flip over to cook the other side. Make sure the patties are cooked through. Drain on an absorbent towel. Set aside.

Place chilies, vinegar, water, sugar and salt in a saucepan over medium-high heat. Bring to boil. Simmer 2 minutes. Remove from heat. Leave to cool completely.

Place cucumber, carrots and coriander (cilantro) leaves in a large bowl. Season with salt. Toss. Set aside.

Heat butter in a pan over medium-low heat. Place the buns in the pan. Make sure the cut sides face down. Toast buns until they are crisp and brown. Set aside.

Spread the base of the burger bun with 1 tablespoon butter chicken sauce. Top with cucumber salad, chicken patty, ½ tablespoon butter chicken sauce, more cucumber salad and 1 pickled green chili. Spread the top of the bun with 1 tablespoon butter chicken sauce and set it on the burger.

Repeat with the remaining ingredients to make 3 more burgers. Serve with masala french fries if you like.