Place the flour in a bowl and make a well in the center. Add the yeast with a bit of sugar and 2 tbsp of the lukewarm milk to the well. Stir slightly and let the yeast activate for about 10 minutes.
After the yeast is activated, add the remaining lukewarm milk, sugar, salt, softened butter, and the egg to the yeast mixture. Knead everything into a smooth dough until it pulls away from the sides of the bowl. Cover and let it rise in a warm place for about 30 to 60 minutes until it has doubled in size.
Meanwhile, prepare the filling: melt the butter in a pan, add the diced apples, sugar, and cinnamon. Cook the mixture over medium heat for about 7-8 minutes until the apples are softened. Let the filling cool down.
After the dough has risen, divide it into ten equal portions (about 50 g each). Roll each portion into a triangle, place a teaspoon of the apple-cinnamon filling at the base, and fold the dough over. Make several cuts on the remaining dough so that, when rolled up, the cuts are visible on top.
Brush the crescents with a mixture of whisked egg yolk and 1 tsp of milk.
Bake the crescents in a preheated oven at 180°C (350°F) for about 15-20 minutes until golden brown. After baking, let them cool, cover with a clean cloth, and dust with powdered sugar.
