Cut the top of the tomatoes and chop them roughly into smaller pieces. Or pulse for few times in your blender to make a coarse slush. I keep the skin, hence in this method you will find the end product with bits of skin in every spoonful. If you would rather prefer a smooth paste, I would suggest peeling the skin before hand. Bring some water to a boil, add the tomatoes and let it sit in a closed pan for 5 min or so. Remove, peel the skin and use.
I used a 3 liter pressure cooker. Add 1 tbsp oil ( or even 2 tbsp if you like). I would recommend Sesame oil for a traditional taste.
Layer the tomatoes on top. If you want to use garlic/onion/or both, mix it along with tomatoes and proceed.
Add the dry spices - chili powder, salt, turmeric, fenugreek and asafoetida next on top of the tomatoes. Note: Please DO NOT add the spices first since it will burn. It should not touch the bottom of the pan.
Cook them at med-high flame for 20-25 minutes for 30+ whistles. Forget the whistles, just go with the time. Also make sure you are around to check your pressure cooker when you are first making this recipe just to know if it's working properly. If the first whistle doesnt come within 2 minutes, check your cooker to see if the steam is not escaping the sides/ or if your safety value is not working. Since we are going with time for this recipe, making sure it's working optimally is essential to prevent burning.
Switch off and open cooker after the pressure settles.
Check to see if your thokku is in a perfect consistency of your choice.
Depending on the variety/quality of your tomatoes, it might be more watery or thicker than this recipe picture. Mine was almost perfect.
Since I needed it a little bit thicker, I placed the cooker again on high heat You can also at this point do a taste test and add more seasoning if needed.
for another 5 minutes (or so) until the desired consistency. If your tomatoes were already too thick when done, I would suggest reducing the cooking time next time around. This is why its imperative to hang around the area in order to make sure nothing is burning :)
While that's happening, heat up the remaining oil and once hot, add the mustard seeds.
When it pops, add it to the prepared thokku.
Mix well until blended.
Bring it to room temperature and store in a glass bottle. It keeps well for weeks in the fridge (mine is on its 2nd week and going great!)