Dissolve the yeast in some milk. Put flour, 50 grams of sugar and salt in a bowl and make a depression in the middle. Add the yeast-milk mixture. Sprinkle with some flour and let it rise covered in a warm place for 30 minutes.
Add fat and egg and knead to a smooth dough. Leave to rise for another 30 minutes. In the meantime, peel and quarter apples and remove the core. Cut apples into small pieces.
Mix with 30 grams of sugar, cinnamon and lemon juice and let it stand for ten minutes. Roll out the yeast dough to a one centimetre thick plate (45 x 30 centimetres). Spread with the apple mixture and roll up from the transverse side.
Brush the edges of the dough with egg white and press down. Cut roll into 1 1/2 thick slices. Let the snails rise for another 15 to 20 minutes. Fry them one after the other in hot frying fat until golden brown. Drain on kitchen paper and turn in the remaining sugar while still warm.