How to make
Peel the apples and grate them (or dice them). Put the butter in a pan and melt it, then add the apples to it. Leave on the stove for about 3-4 min.
Next, add the walnuts, cinnamon, sugar and raisins. Return to the stove and leave there until the apples soften well. Once they do, remove from the stove and leave aside until the mixture cools completely.
Once cooled, roll out the puff pastry lightly. The reason for this is to prevent the puff pastry from rising too much. Pour the filling with apples in the middle along the entire length of puff pastry. On both sides of the filling, cut the puff pastry into strips. The strips need to be at a slight angle.
Once you've cut the strips, start closing the strudel by alternating: cover with a strip from the left side, place a strip from the right side on top and so on until you've closed the entire strudel.
Put baking paper underneath the strudel. Smear with beaten egg on top and bake about 40 min. at 360°F (180 °C). Optionally, sprinkle with powdered sugar.