Take the yeast in a bowl along with 1 teaspoon of sugar.
Add lukewarm water and keep aside for about 5 minutes till it becomes frothy and rises.
In another bowl take rest of the ingredients and yeast and mix well till you get a ball.
Tip onto a floured surface and knead till you get a smooth and elastic dough.
Return to a bowl and cover with a damp cloth and keep in a warm place till it doubles up in volume .
Meanwhile heat 2 tablespoons of oil in a pan and saute the onions till they turn pink in colour.
Add the chopped ginger and garlic and stir for a minute.
Add the coriander and chilli powder and stir for a minute.
Add the chicken and potatoes and mix well.
After a minute, add the garam masala powder, chopped leaves and mix well.
Finally add the tomato sauce and mix well.
Switch off the heat and let the mixture cool.
Flatten the dough with your hand and knead for a minute.
If it is sticky, take a bit of oil in your hand and knead.
Form small balls and flatten them using a rolling pin or with your hand and place some filling.
Lift the edges and bring towards the centre and seal them.
Form into a desired shape. Place these on a greased tray. Keep aside for 15 minutes.
Meanwhile preheat the oven to 180C. Brush the buns with egg yolk.
Bake the buns for about 20 minutes or till they turn golden brown.
Eat when its warm. They taste better when warm... :-).