Inspired from Bon Appetit
3/4 cup plus 1 tablespoon apple juice
1 tablespoon Calvados
1 cinnamon stick
1 vanilla bean, split in half lengthwise
3 cups 1/2 inch apple cubes (I used a combination of Granny Smith and yellow delicious)
1/3 cup brown sugar
1 teaspoon cornstarch
9 sheets of filo dough, defrosted
1/2 cup unsalted butter, melted
6 tablespoons Panko
2 tablespoons sugar
4 ounces white chocolate chopped
1/4 cup cream
1 teaspoon Frangelico
1/2 teaspoon vanilla
1/2 cup powdered sugar, sifted
Combine juice, Calvados, cinnamon and vanilla bean in a saucepan. Simmer for 3-4 minutes till reduced by half. Discard cinnamon and vanilla bean. Add apples and sugar and cook till apples are tender. Mix cornstarch in the 1 tablespoon of apple juice, then add to apples and cook till liquid boils and thickens. Allow apples to cool.
Preheat oven to 375º. Line baking sheet with parchment and set aside.
Mix the Panko and sugar in a small bowl. Set aside. Take filo out of box, cut 3-4 inches off of 9 sheets of filo (making more of a square shape than a rectangle...dimensions don't have to be exact), put the rest away for another use. Cover the 9 sheets with plastic, then a damp towel.
Place a dry kitchen towel on the counter. Place one piece of filo on the towel and brush lightly with melted butter. Repeat with second sheet of filo. After brushing the second sheet with butter, sprinkle with a scant 2 tablespoons of Panko sugar mixture, then repeat two more times, brushing and layering two sheets with butter, then sprinkling with Panko. With last 3 sheets, just layer and brush each with butter.
Spoon filling along side of filo stack closest to you, in a strip about 3 inches wide starting an inch away from one side and extending almost all the way across. Use towel to roll dough up like a jelly roll. Push any escaped apples back into strudel and place seam side down onto parchment paper lined baking sheet. Brush exposed filo with butter, then cut slashes across top on the diagonal (place where you'd be cutting slices after it's baked), cutting almost through the top crust.
Bake for about 30 minutes, till golden. While cooling make icing.
In microwave safe bowl, melt chopped white chocolate and cream stopping and stirring every 15-20 seconds till smooth. Add vanilla and Frangelico, then powdered sugar. Whisk till smooth. Place in quart ziplock bag and seal. Allow to cool. Snip off corner and drizzle over cooled strudel.