In a large bowl, whisk together all the dry ingredients. Add the butter and lukewarm water and knead till you have a soft dough, a little sticky is OK. Add more flour if needed. I used almost 1/2 cup extra.

Oil the bowl and leave the dough to double for an hour.

Meanwhile, to make the filling, heat oil. Fry the garlic and curry leaves briefly. Add the onion and saute till wilted.

Add the spice powders and cook for a minute. Add the mashed potato and the tuna. Break down with the spatula and mix well till done. Adjust seasoning and switch off.

Prepare a large tray or two with parchment paper. Set aside.

Once the dough has proofed, punch down the dough and divide into 8 balls. Divide the filling equally as well.

Roll one ball into a round. Put one part of the filling and seal (as per above step by step). Press well and keep on the prepared tray. Complete the remaining in the same process. Cover and allow it to rise for around 20 minutes.

Meanwhile, preheat oven to 180 degrees. Brush on top of the buns generously with the beaten egg.

Bake for 25 minutes. Turn on the top grill and grill for 3-5 minutes till the top is browned. Take off, allow to cool slightly and enjoy with some ketchup.