Clean the squid well and cut into long strips. Alternately, get squid rings and cut into half.
In a large pan, heat oil and crackle the mustard seeds.
Add the sliced onion and sauté for about 2 minutes. Add the crushed ginger and garlic and sauté till the onions are light golden brown.
Add a sprig of curry leaves and the tomatoes. Sauté on medium heat till the tomatoes have softened well.
Add the powdered spices except fenugreek and continue to cook on low heat till the mixture comes together and oil starts to appear at the edges.
Add the squid slices and season with salt. Mix well and cook for 2 minutes. Add ½ cup water and bring to boil (add more water if you want more gravy). Lower heat and simmer till the squid is cooked well.
Add the fenugreek powder and the remaining curry leaves. Mix well and remove from heat.
Garnish with coriander leaves and serve hot.