In a small bowl, dissolve yeast in warm water. In a large bowl, combine milk, butter, 1/3 cup sugar, egg yolks, salt, yeast mixture and 3 cups flour; beat until smooth. Stir in enough remaining flour to form a soft dough (do not knead)., Place in a greased bowl, turning once to grease top. Cover and let rise in a warm place until doubled, about 45 minutes., Punch dough down. Turn onto a lightly floured surface; knead about 10 times. Divide dough in half. , Roll each portion to 1/4-in. thickness; cut with a floured 2-1/2-in. round cutter. Place about 1/2 teaspoon jelly in the center of half of the circles; brush edges with egg white. Top with remaining circles; press edges to seal tightly. , Place on greased baking sheet. Cover and let rise until doubled, about 45 minutes., In an electric skillet or deep-fat fryer, heat oil to 375°. Fry doughnuts, a few at a time, 1-2 minutes on each side or until golden brown. Drain on paper towels. Roll warm doughnuts in remaining sugar.