Roll the puff pastry into a large rectangle roughly the size of the baking sheet pan. Place into the refrigerator until ready to use.
Core and slice the apple into small pieces.
In a large bowl combine the lemon juice, brown sugar, bourbon, cinnamon and mix evenly. Toss the apples and cranberries in the sugar mixture gently until evenly coated. Add the cornstarch and toss again.
Remove the puff pastry from the refrigerator and pour the apple and cranberry mixture into a line in the center of the puff pastry in the direction of the longest side. Cut inch long strips on each side of the line of apples and cranberries. Starting from the top fold the top edge over the end of the apple mixture. Alternating sides overlap each of the strips in a braid-like fashion.
Mix the egg and milk together. Brush the egg wash mixture over the top of the strudel. Bake for 35-45 minutes until golden brown. Allow to cool before slicing.