Soak chana dal in water for 2 hours.
Cook the chana dal in pressure cooker by adding double the water (3 cups) and 1/4 tsp salt.
In a pot mix cooked chana dal, jaggary and sugar. Keep it on a burner on a medium flame and make puran (stuffing). Stir continuously.
Stir till puran is done. (see notes)
Add cardamom powder and nutmeg powder.
Take cooked puran on a sifter. Sieve the puran through the sifter by a spoon to remove all the lumps. Keep it aside.
On a plate mix all purpose flour, 1/4 tsp salt. Knead the dough by adding 3/4 cup of water gradually. Add 5 tbsp oil gradually. The dough should be very soft.
Make small balls of the dough about 2 inch diameter.
Divide the puran by making oval shape balls.
Take one dough ball and flatten it a bit and put one puran ball in it.
Press the puran ball in the flattened dough.
Cover the puran by flattened dough from all the sides.
Roll the poli gently by sprinkling all purpose flour.
Roast it on a pan from both sides.
Cool it on a cooling rack before storing it.