Take yeast in a small microwave proof bowl. Add a pinch of castor sugar and 2-3 tablespoons warm water and mix. Place the bowl in the microwave and heat for 5 seconds. Set aside to activate.
Sieve together flour into a bowl. Add remaining sugar and salt and mix well.
Add activated yeast and mix. Add some milk and knead into soft dough.
Add butter to the dough and knead, dusting with some flour, till it becomes soft. Transfer into another bowl, cover with a cling film and set aside to prove for 1 hour.
Transfer the proven dough onto the worktop, dust some flour and roll into a thick sheet. Cut into donut shaped roundels with a donut cutter and discard the center of the donuts.
Now heat oil in a kadai & deep fry the donuts.Keep it aside to cool down.
Melt the dark chocolate with little butter.Now dip one side donuts into the melted chocolate & garnish with sprinkles.Keep in the refrigerator for 15-20 mins till the Chocolate sets....Enjoy your donuts.