Mix half of the butter with evaporated milk, sugar, Cardamom powder and yogurt, beat lightly with a beater.
Melt the other half of the butter and fry the flour till light golden in color about 2 mins, add in the evaporated milk mixture and beat well on slow heat.
When bubbles start to come on top, immediately add in powder milk, keep stirring, mix well, reduce heat, cook till it becomes slightly golden like khoya, remove, slightly cool for 2 mins.
Do not let it cool too much, make it into round balls, slightly flatten like nan khatai.
Press with the mould slightly, sprinkle crushed pistachio.
If the mixture becomes cold and pera doesn’t form, add 1 tbsp of evaporated milk.