First, in a large bowl soak 1 cup of toor dal for 1 hrs. Cook the dal with 1-1/2 cups of water until soft and well cooked. Mash dal with a masher and make a smooth paste and keep aside.
Heat pan and add cooked dal and 1 cup jaggery in it.
Stir continuously till the water evaporates from the mixture.
Then add cardamom powder until well combined to make the puran poli filling
Then continue stirring the puran poli mixture until the dal mixture begins to thicken and leaves the sides of the pan. At this point turn off the heat and allow the puran poli mixture to cool completely.
Now make the dough. Add 2 cup wheat flour and 2 tbsp oil into a large bowl; combine it with little water at a time and knead until the dough gathers together to form a firm dough mixture.
Cover and let the dough sit in a cool place for around 15 minutes.
Take lemon size balls from the dough. Roll out the puran poli dough into 3-inch diameter circles.
Place a portion of the puran poli mixture into the center of the circle.
Bring the edges of the circle towards the center and fold over to cover the entire filling; making sure the edges are all sealed well by pinching them together if there is any opening.
Flatten the stuffed dough; dust over a little flour and roll gently into a 4-inch diameter circle taking care not to put too much pressure as the puran can come out of the dough.
Place puran polio on tawa on medium flame, then rolled puran poli onto the tawa to cook until golden brown on both sides.
Serve the Gujarati Puran Poli hot with ghee smeared on the top.