Wash the Taro roots or arvi or arbi nicely with clean water atleast 2-3 times, to remove all the mud and dirt.

Now transfer the Taro roots or arvi or arbi to a pressure cooker and add some water to it. Pressure cook for 1 whislte over high flame to boil the Taro roots or arvi or arbi.

Allow the pressure cooker to cool and then open the lid and take out the boiled Taro roots or arvi or arbi in a plate. Peel off all the boiled Taro roots or arvi or arbi and chop them into small pieces.
Take the yellow mustard seeds, garlic petals and whole-dried red chillis in a mixer jar. Add 2 table spoon water to the jar and then grind the ingredients together to form a fine paste.

Now heat some mustard oil in a kdhai and add fenugreek seeds to it when the oil is hot enough for cooking. Allow the fenugreek seeds to crackle and change colour. Avoid the fenugreek seeds fom turning black in colour.
Add paste garlic and whole-dried red chillis to kadhai. Stir and cook the paste for a few seconds.

Now add all the powder spices (turmeric powder, red chilli powder, cumin seeds powder, black pepper powder and coriander powder) and salt to the cooking ingredients. Stir, mix and cook all the ingredients together for a few seconds.
Add the chopped tomato pieces and again stir, mix and cook all the ingredients together. Cook the ingredients together till the tomato pieces become soft and oil begins to separate from the cooking ingredients. Mash the tender tomato pieces with the ladle.

Now add the chopped pieces of boiled taro roots or arbi or arvi. Stir and mix the chopped pieces of boiled  taro roots or arbi or arvi with the cooking ingredients. Then squeeze the 1/2 lemon and add it's juice to the cooking ingredients in the kadhai. Mix it with the cooking ingredients. Now add water to the kadhai.

The amount of water should be slightly more than required for gravy. This is required because the boiled taro root pieces or arvi pieces or arbi pieces soak up the gravy when

Then squeeze the 1/2 lemon and add it's juice to the cooking ingredients in the kadhai. Mix it with the cooking ingredients.
Now add water to the kadhai. The amount of water should be slightly more than required for gravy. This is required because the boiled taro root pieces or arvi pieces or arbi pieces soak up the gravy when cooled after cooking.
Allow the gravy or taro root curry or arvi ki sabji or arbi ki sabji to come to a boil.