First, either crumble fresh yeast into the flour or stir dry yeast with 5 g sugar in warm milk and let stand for 10-15 minutes. Add 100 g flour. Stir for 3-5 minutes to form a smooth dough. Let the dough rise until it doubles in volume.
Add the remaining ingredients to the risen dough. Knead for another 3-5 minutes until the dough is uniform and smooth.
Divide the dough into 10 equal parts and with floured hands, shape each part into a ball. Place the balls on a lightly floured board and let rise in a warm place until doubled in size.
Fry the balls,at an oil temperature of 170 °C for 5-6 minutes until golden brown. Turn them frequently to the other side so that they brown evenly. Drain well.
Using a sharp kitchen knife, briefly score the side of each doughnut and fill each with 1 tsp of jam.
Sprinkle the doughnuts with powdered sugar.