Take 2 tablespoons of the milk in a bowl and add 1 tsp of the sugar and the yeast. Mix well and set aside.
In the bowl of a stand-mixer with the dough attachment, add the flour, salt, sugar and the remaining milk. Mix till the flour is moistened and let it sit for 5-10 minutes.
After 5-10 minutes, your yeast mixture should be light and fluffy. Add this to the flour and start mixing at a low speed, slowly increasing to high. Knead for 2-3 minutes, then add the condensed milk. Knead for another 2-3 minutes. In case your dough is too dry, add 1-2 tbsp of water.
Lastly, with the mixer on low, gently add the soft butter. Once poured, increase the speed to high and knead till a very smooth and elastic dough forms, it should not stick to the sides of the bowl and will be very smooth.
Roll the dough into a smooth ball and place it in a greased bowl. Cover and let it proof till it is doubled in size. Time can range from 45 minutes up to 2 hours depending on the temperature of your kitchen. Do not over proof your dough.
Once doubled in size, drop the dough to a clean and floured surface, roll the dough out using a rolling pin to approximately an 2 cm thickness. Take a round cookie cutter (I used a 3 inch cutter) and cut out as many circles as you can. You can re-roll the scraps once and make more doughnuts, I do not recommend doing this more than once.
Place the cut out doughnuts on a floured tray and cover with a damp cloth. Let them rise for another 30-45 minutes or until almost doubled in size.
Fry the doughnuts
In a large heavy bottomed pot, fill enough oil so that it comes 3/4 way up. Let the oil heat up to 175 C and fry the doughnuts at the most 3 at a time. Let them cook for 2-3 minutes per side or until light golden brown.
Coat the fried hot doughnuts in caster sugar for the classic look.
Blend all the ingredients for the filling in a high powered blender till it becomes a smooth paste.
Fill the doughnuts:
Use a knife or skewer to poke a hole through the donut, only pierce halfway through the donut and be gentle not to break it.
Fill the Pistachio Rose cream into a piping bag fitted with a narrow piping tip. Squeeze the filling into the warm doughnut till it is full.