Add whole wheat flour, salt to a mixing bowl. Add water in a steady stream and knead them until well combined. Add the oil and knead them again until the dough is soft, supple and not sticky. Cover and set it aside for atleast 20 minutes before you make the paratha.
In a Stand Mixer
Add the whole wheat flour, salt to the bowl of the stand mixer. Add 1/2 Cup of water and start the mixer at Speed 1. In a steady stream add the remaining water. All the kneading hook to do the job. Stop the stand mixer and using a silicone spatula, move the dough from the edges to the middle. Start the stand mixer again, add oil and allow it to knead until well combined. The whole process will take about 5 minutes. Cover and set the chapathi dough aside for atleast 20 minutes.
To Prepare Paratha Filling
This can be done in 2 methods -
In a food processor, add cooked kidney beans,coriander leaves, ginger, onions, cumin powder, chilli powder, garam masala, salt and whizz until the kidney beans is mashed and the rest of the ingredients are well combined. Heat oil in a pan, add the kidney beans mixture, lemon juice and cook for a few minutes until any water left is evaporated.
Mash the Kidney beans and set aside. Finely chop the the onions, coriander leaves and set aside.
Heat Oil in a pan, add onion, ginger paste and saute for 2 minutes. Add the mashed kidney beans, spice powders,lemon juice, salt to the pan and cook until well combined.
How to make Rajma Paratha
Divide the dough into 10 equal portions. Pick one portion of dough at a time, dust some flour and spread them with the roller into thin disk of 5cm or so. Spread 1/2 a tsp of oil in the middle of the rolled dough, place the kidney beans/ rajma paratha mixture right in the middle leaving space in the edges to seal.
Starting right from the edge, begin pleating and seal the filling mixture with the dough. Dust some flour and roll the dough gently, ensuring the filling doesn't come out.
Heat a non-stick pan / tava to a high temperature. Place the rolled Rajma paratha on the tava and cook for a 1-1.5 minutes or so. When the base is cooked, flip the paratha and cook again.
Spread a teaspoon of oil on part cooked paratha. Flip again and you will find the paratha cooked nicely with a couple of charred/black spots. Spread some more oil and you will find the paratha puffs up really well.
You may even use spatula's to press the edges of the dough, just to ensure they cook well.
Remove the cooked paratha's from the flame into a casserole and keep them covered.