Heat the oil in a large non-stick pan over medium heat and cook the onion until it starts to soften (about 4 minutes).
Add the garlic and ginger paste to the pan and stir through. Stir in the dry spices (cumin, turmeric, cinnamon and garam masala). Add a splash of water if it starts to stick. Cook for a further minute.
Meanwhile, add the cashews and plant milk to a high speed blender, and blend smooth.
Add the contents of the pan to the blender, along with the tomato passata, sugar and salt. Whizz until smooth.
Pour the mixture back into the pan. Tear up the seitan ‘chicken’ into chunks and add them to the pan. Simmer for 10 minutes, or until warmed through. Taste test and adjust the seasoning, to suit.
Garnish with coriander leaves and serve with rice and pieces of naan bread. We also love to serve some roasted cauliflower on the side.