Take the dry ingredients (flour, yeast, salt, sugar, and baking powder) in a large Pyrex bowl and whisk together to combine.
Add the yogurt and mix it in.
Add the milk little by little and knead the flour until it becomes a smooth ball. (8-10 minutes)
Lightly oil the bottom and sides of the instant pot and place the dough ball in it. Roll it around to coat the surface with oil. Put the lid in place and set the instant pot on the yogurt setting (normal) for one hour. Alternatively, you can put the ball of dough in a greased Pyrex bowl, cover it with cling foil and keep it in a dark place to rise. It will take 2 hours approximately for the dough to rise and double in size.
Once the dough has doubled, it will be very soft and light. Carve it into 8 pieces and shape it into balls. Cover these balls with a damp tea towel and allow them to rest for 15 minutes.
Now, take each ball and with a rolling pin, roll it it out into an oblong or round disc. You won't need any dry flour at this point because the wholewheat dough is very pliable and will not offer much resistance. Sprinkle a few nigella seeds on one side and roll over it so the seeds stick. Keep the discs covered with a damp tea towel till they are ready to cook.
Place a griddle on the stovetop and heat it to moderate heat. Take one rolled out disc and brush the other side with water. Press this side face down on the hot griddle so that the disc sticks to the griddle. Allow the dough to cook for 30 seconds to 1 minute. The dough will form bubbles and air pockets on the side that's up, and after about 30 seconds, it will start leaving the sides. With the help of a spatula, flip the naan and cook on the other side. Repeat for all the discs.
If you don't want to flatten those air pockets, invert the griddle after pressing the water side down and cook the naan directly on the open flame until the edges start to char slightly. However, you can do this only if you have a stovetop with gas burners.
Once all the naans have been cooked, brush them with ghee or butter and serve hot with your favorite curry.