Clean and devein the prawns. Put the prawns in a bowl and sprinkle salt. Set them aside.
Now let's make red chillies paste. For that soak whole red chilies in vinegar and brown sugar for 1 hour.
After an hour grind it in mixer. Take a spoon of this mixture and add this to cleaned prawns.
To this add lemon juice and crushed black pepper powder. Keep aside to marinate.
Using a dry pan over medium heat, toast the cinnamon, cloves, cumin seeds and whole peppercorns until they begin to release their aroma. Take off from the heat and cool.
Grind the ginger, garlic, and toasted spices into a smooth paste using the that remaining red chillies paste. You can do this in a mortar and pestle also. Take out in a bowl.
Heat the oil on a medium flame in a wok or pan. Add the prawns and stir fry it till it becomes opaque. Remove from the pan and set them aside.
In the same pan add oil and crackle mustard seeds. Add chopped onions and fry the onions until they are light brown. Add the tomatoes and fry until soft.
Now add the red paste, sugar, and salt to taste. Fry until the oil begins to release from this paste.
Add the marinated prawns to this spice mixture, mix well and cook for 2 to 3 minutes. If required add some water and cook it on low flame.
Once cooked, add worcestershire sauce. Mix well and add a small piece of jaggery before switching off the flame. Garnish it with fresh coriander leaves.
Serve with hot plain boiled rice or chapati