Wash bitter gourds properly and then use a peeler or knife to scrape off the skin. (I don't scrape off all skin, I keep some on.)
Cut off the portion near both ends and then cut approximately 1-inch pieces.
Scoop out the seeds and white flesh from the pieces, apply some salt on them, and then wash the pieces thoroughly after 15-20 minutes.
Meanwhile, take besan and jowar flour in a dry bowl.
Add ajwain, haldi, hing, red chili powder and salt, and mix it well using a dry spoon.
Arrange the karela pieces in a cooker's vessel and then pour in the flours' mixture in them. (Don't press the stuffing as it doesn't taste too good after cooking if the flours are packed in too tight.)
Cook in a pressure cooker on medium flame for 10-15 minutes (4-5 whistles).
Heat a pan and add 2 tbsp oil. (I usually use iron kadai because karela comes out nice and crispy, but it turns black. I didn't want it to look black in the pics, so just this once I didn't use iron kadai.)
When the oil heats up, add mustard seeds.
When the mustard seeds spultter, add a pinch of hing and haldi.
Transfer 1-2 tsp of the tempering (tadka) in a separate bowl.
Add the pressure-cooked karela pieces to the kadai, and stir.
Sprinkle some salt and drop in a little bit of tadka that you had set aside from both sides of the pieces to eliminate the floury taste from the stuffing.
Cook on medium flame for about 10 minutes while stirring intermittently. (You can add some oil while the sabzi is cooking if you feel it's turning out too dry.)
Add chopped coriander, stir, and cook for about a minute before turning off heat.