Devein and wash the prawns/shrimps well. Discard the shells if you like.
Grind all the ingredients for the Mustard Sauce into a smooth paste with water. Arrange the prawns in the pan you like to cook them and then add the blended paste.
Also add sugar, salt, and about a cup of water, ie. 200 ml. Mix well and place the pan on medium heat.
Cover the prawns and allow them to cook in the mustard sauce for 5 to 8 minutes or until they are tender.
Once done, check for seasoning. Reduce the extra liquid by cooking on high heat, we are looking for a thicker sauce or gravy.
Finally, garnish the dish with coriander leaves and switch off the heat. Prawns in Mustard Sauce are ready for serving.