Put 125ml warm water into a bowl and sprinkle over the yeast and 1 tsp of the sugar. Leave for 10-15 mins or until frothy. In a larger bowl put the flour, remaining sugar, ½ tsp salt and baking powder. Mix together then make a well in the centre in which to pour the melted butter, yogurt, nigella seeds and yeast mixture. Stir well, then start to bring the mixture together with your hands. If it’s very wet add a spoonful of flour but if it’s dry add a splash more warm water. It should be a very soft dough but not so wet that it won’t come together into a ball of dough. When you’re happy with the consistency, start kneading, first in the bowl then transfer the mixture onto a well floured surface and continue to knead for 10 minutes or until smooth and elastic but still soft. Grease a large bowl with extra melted butter or ghee then shape the dough into a ball and place in the prepared bowl. Cover and leave in a warm place for about 1 hr or until doubled in size.