Roughly chop the vegetables, transfer to a small food processor, and add 3 tablespoons of water - process to a slack paste. Tip into a small bowl and leave on one side. Put the garlic oil and ginger into the same food processor and add 4 tbsp water – process until smooth and spoon into another small bowl.
Heat the oil in a wok or sturdy pan set over a medium heat. Combine the cumin with the cinnamon and chilli flakes and add to the pan in one go. Swirl everything around for about 30 secs until the spices release a fragrant aroma.
Add the vegetable paste – it will splutter in the beginning. Fry until the water evaporates and the vegetables turn a lovely golden - this should take about 7-8 mins. Add the garlic oil and ginger paste and cook for another 2 mins – stirring all the time.
Stir in the turmeric, and sugar and continue cooking for 20 secs before tipping in the tomatoes. Continue cooking on a medium heat for about 10 mins without a lid until the tomatoes reduce and darken.
Cut the chicken thighs into 3cm chunks and add to the pan once the tomatoes have thickened to a paste. Cook for 5 mins to coat the chicken in the masala and seal in the juices, and then pour over the hot chicken stock.
Simmer for 8-10 mins without a lid until the chicken is tender and the masala lightly thickened – you might need to add an extra ladleful of stock or water if the curry needs it. Sprinkle with chopped coriander and serve with fluffy basmati rice.