Cut the jack fruit into small chunks about an inch by inch. Wash thoroughly under running water and then boil in a sauce pan with a little bit of water. Make sure that the fruit is just a little bit soft and should not over boil. I actually did it in a pressure cooker only till the whistle was about to blow when I turned off the gas.
In the mean while dry roast the coriander seeds and grind it in coarse powder. Do the same for the panch phoron. Basically you just need to pulse the spices or use a mortar and pestle to grind it to a desired consistency. Then use a bit of water to make it into a thick wet paste.
Wash the mustard seeds thoroughly and then keep them soaked for 15 minutes. Then grind the mustard seeds with a little bit of water into a fine paste.
Make a paste of the garlic cloves too. Again, it need not be a fine paste. A little bit of garlic chunks here and there is quite nice.
Once the jackfruit has become a bit soft, drain the water and place the jackfruits in a large strainer or in a muslin cloth which will absorb all the water. You have to make sure that there is not water left in the fruit.
Wash the green chilies also under running water and then using a muslin cloth absorb all the water. Dry the green chilies out completely.
Now we can finally start the cooking process. In a large kadai, which will accomodate all the green chilies, take about a quater of the oil and heat it. When it starts smoking, add the turmeric powder, salt and lower the heat. Add 2 tbsp of the panch phoron and coriander seed paste.
Increase the temperature to medium and cook the spices till the raw smell of the turmeric goes away (in about a minute). Add the green chilies in the same kadai and stir properly so that the chilies are coted with the spices.
Cook for about 2 - 3 minutes and turn off the heat. Take the chilies out and spread them on a large plate and cool them down.
Take a large sauce pan or any vessel to heat the rest of the mustard oil. When the mustard oil has become hot, almost smoking, turn it off and let it cool down completely.
When everything has cooled down, take a vessel large enough to mix all the ingredients.
First take the green jackfruits, then the chilies, then the mustard paste, garlic paste, rest of the spices and finally pour in the oil. Mix them all together nicely without mushing the jackfruits. Wear gloves if you want to and then use your hands to do this bit for a proper mixing.
Once everything has been thoroughly mixed, put them in glass or ceramic jars and cover with a muslin cloth and keep in the sun for a couple of days.
Since the green jackfruit is already cooked, it is not needed to mature for more number of days. Also, you need to check after a day if the jackfruit has soaked up all the oil or not. If so, then heat some more mustard oil, cool it down and pour it over the achar.
Echorer achar is ready to eat.