Heat the oil in a large pot on medium heat. Sprinkle in the ajwain or cumin seeds. Add the onions and salt and sauté until the onions are light golden brown. Add the garlic and sauté for a few seconds.
Stir in the chilli powder, tomatoes, ground cumin, ground coriander, garam masala and turmeric and simmer until the sauce thickens.
Pour in the cream and add the prawns. Simmer until the prawn tails start to curl and remove from the heat. Add some boiling water if the sauce is too thick.
Sprinkle the black pepper over the prawns, garnish with fresh coriander and curry leaves and serve with bread.