In a large bowl, combine warm milk and butter. Stir until the butter melts completely. Add sugar, egg yolk, whole egg, salt, and the yeast mixture. Mix well, then add 3 cups of flour and beat until smooth.

Gradually add the remaining flour until a soft dough forms. The dough should be slightly sticky but easy to handle. Do not knead the dough yet.

Place the dough in a greased bowl and turn it once to coat the top. Cover with plastic wrap and let it rise in a warm place for about 1 hour or until doubled in size.

Punch down the dough and transfer it to a floured surface. Knead lightly about 8 times. Divide into two portions and roll each to 1/4-inch thickness. Cut into circles using a round cutter.

Place 1/2 teaspoon peanut butter and 1/2 teaspoon jelly in the centre of half the circles. Brush edges with egg white, cover with another circle, and press edges tightly to seal.

Place the filled donuts on a greased baking sheet. Cover and let them rise again until doubled in size.

Heat oil to 180°C. Fry the donuts in small batches for about 2 minutes on each side until they turn a beautiful golden brown. Remove and drain on paper towels. While still warm, roll the donuts in granulated sugar for that classic finish.