Heat some oil in a large pan and add the onion until soft and translucent.
Add all the spices, the ginger and the chili flakes to the onion until it becomes fragrant. Add the pears and the sugar and about 100 ml water. Leave to cook until the pears have softened.
Add the mango, salt and red wine vinegar. Let it simmer until the desired thickness. Remember that it will thicken a bit when it cools. Keep the chutney in sterilized jars in a dark spot until you need it.
For the burger:
Score the chestnuts with a sharp knife on the round side. Cook for about 3 minutes, drain and peel when still warm. Also remove the brown fluff from the inside. Cut in small pieces.
Put the beef, the chopped chestnuts, egg, breadcrumbs, pepper, salt and ham together in a bowl and mix to combine well. If too wet add a bit extra breadcrumbs. Make 4 burgers of the mixture.
Heat the oil and fry the burgers on medium heat until brown and cooked through.
In the meantime fry the bacon brown and crispy. Leave to drain on paper towel.
For making the burgers start with a small layer of sauce (mayo or otherwise of your choice), top with the lettuce and place the burger on the lettuce. Top the burger with mango chutney and crumble the bacon over it. Serve with some extra chutney.
Notes
In the nutritional information the mango chutney is not taken into account as you do not use all of the mango chutney