Preheat the oven to 200C/400F/Gas 6.
Cut a 6cm/2½in piece of squash and peel, then cut into four 15mm/¾in thick slices and set aside. Cut another piece (about 300g/10½oz), peel and cut into 1cm/½in cubes.
Season the chicken breast with salt and black pepper.
Heat a frying pan until hot. Add a knob of butter, the olive oil and the chicken breast skin-side down and fry on each side for 1-2 minutes, or until golden-brown. Add the squash slices and place in the oven for 15 minutes, or until both are cooked through.
Meanwhile, heat a sauté pan until hot. Add the remaining butter and, when melted, cook the shallot, garlic and the cubes of squash. Cook for a couple of minutes.
Stir in the sugar and cook until it starts to caramelise, then add a few tablespoons of water and the ginger, turmeric, fenugreek and black onion seeds. Cook for another couple of minutes.
Add another 3-4 tablespoons of water and stir to combine, then add the chilli, coriander and a generous pinch of salt. Remove from the heat and stir in the mango chutney.
To serve, place two slices of pumpkin on each plate, top with a chicken breast and then spoon some pickle alongside.