Place the flour in a bowl, make a well in the centre. Crumble the yeast into it with 1 tbsp sugar and 3 tbsp lukewarm milk. Mix together and allow to stand in a warm place for about 15 minutes.
Add the remaining milk, sugar, egg yolks, room temperature butter and a pinch of salt to the dough and knead into a smooth dough in a food processor with a dough kneading attachment. Mix until the dough appears to detach easily from the sides of the bowl.
Allow the dough to rise in a warm place until it doubles in size (approx 30-60 minutes).
Roll out the dough into 3/4 inch thickness on a floured surface and cut of circles approximately 3 inches in diameter using a glass or cup. Allow the cut-out dough circles to stand for a further 10 minutes covered with a dish towel.
Heat the oil to 170°C . Lower the donuts 2 to 3 at a time into the hot oil and fry until they puff up and turn golden brown.
Remove the fried donuts from the oil with a slotted spoon and allow to drain on paper towels.
Allow the donuts to cool then fill them with jam using a decorating syringe with a long thin needle. Sprinkle with confectioners sugar and enjoy!