Add the yeast to warm milk, stir until it is dissolved and then set aside.
In a Kitchenaid stand mixer fitted with paddle attachment, cream together the sugar and butter until the mixture is fluffy. Beat in the egg, egg yolk and salt until incorporated well.
Slowly add 600g flour alternating with adding the milk-yeast mixture. Beat for a minimum of 5 minutes by machine until smooth. The dough will be very slack. If the dough is too soft, add remaining flour 25g at a time until desired consistency.
Place prepared dough into a greased bowl. Cover it and let it rise until doubled in size. 1 to 2 1/2 hours.
Turn the dough out onto a lightly floured surface. Shape into ovals 1/2-inch thickness (1.3 cm). Cut out rounds with 3-inch (7.5 cm) biscuit cutter. Remove the scraps, then re-roll and re-cut. Cover. Let rounds rise until doubled in size. (30 minutes or more)
Heat oil to 175C in large, deep pan. Place the Paczki top-side down (it’s the dry side) in the oil, just a few at a time. Fry 2 to 3 minutes or until bottom is golden brown. Turn them over. Fry another 1 to 2 minutes or until golden brown.
Don’t let the oil get too hot. It will brown the exterior before the interior is done. Test a cool paczki to make sure it’s cooked all the way through. Adjust cooking time and oil heat if needed.
Drain paczki on kitchen paper and roll in granulated sugar while they are warm.
Poke a hole in the side of the paczki then, use a pastry bag, and squeeze in a dollop of a raspberry or strawberry preserves. Then dust with granulated sugar, or icing sugar.
Scoff whole or savour each bite. It is totally acceptable to have a icing sugar moustache or to lick the sugar off your fingers. We won't tell....