Heat the vegetable oil over a medium heat and add the ginger and garlic. Cook for 2 minutes then add the chilli flakes, smoked paprika, turmeric, mustard seeds and curry powder. Cook the spices for another 2 minutes then add the cherry tomatoes and cook until they're beginning to burst.
Pour in the vinegar, chopped tomatoes, brown sugar and season with salt. Cook until all the cherry tomatoes have burst and the sauce has reduced to your preferred consistency.
To Make the Sandwiches
Put the flour, beaten egg and breadcrumbs into separate bowls. Coat the halloumi slices in flour then dip them in the egg. Shake off any excess then coat in the breadcrumbs.
Place an inch and a half of vegetable oil in a small saucepan and heat to about 190°C. Fry the halloumi slices one at a time until browned on both sides, remove on to a paper towel lined plate. Split open the buns and spread the bottom half with mayonnaise and the top half with kasundi then put a halloumi slice in each bun.
Note: The kasundi recipe makes more than you will probably need for your sandwiches. It keeps well in the fridge for at least a week. This means that the nutritional information is slightly out as the kasundi recipe will serve 4-6 rather than 2!