Firstly, take all purpose flour, wheat flour, baking powder, baking soda, salt and sugar in a mixing bowl. Mix well.
Add milk, curd and required water as needed little by little and make a non sticky dough.
Knead well for 10 mins and keep aside for 1 hour. Smear a little oil over the surface.
I used my bread machine for kneading but you can do it in hands.
After that, knead again to smooth and divide into 9-10 equal sized balls.
Chop onion very finely using a food processor or with your knife.
Dust and roll out the dough into slightly thick roti.
Sprinkle little chopped onion below and roll gently to stick the onion in kulcha.
Apply water on the top and place the water applied side to the hot tawa.
Cook covered until the color changes and bubbles appear on top.
Flip and press gently to cook evenly. Let golden spots appear all over. Refer video for stuffing version.
Lastly, smear butter and serve.