Here’s what you will need:
2 1/2 pounds apples, peeled, cored, and thinly sliced (about 7 cups) I used a mix of Granny Smith and Honeycrisp.
1 cup dried cranberries
2/3 cup sugar
1/4 cup all-purpose flour
1 teaspoon ground cinnamon
1 17.3 ounce package frozen puff pastry (2 sheets), thawed
1/4 cup unsalted butter, cubed
About 3 tablespoons milk
Coarse sugar (for sprinkling on the top crust)
2 cups confectioners’ sugar
1/4 cup unsalted butter, melted
4 – 5 teaspoons milk
1 teaspoon vanilla extract
1/2 teaspoon salt
Begin by preheating your oven to 375 degrees F. Lightly grease a 15×10-inch baking sheet. In a large bowl, stir together the sliced apples, cranberries, sugar, flour, and cinnamon. Set aside.
On a lightly floured surface, unfold one pastry sheet. Roll the pastry into a 16×11-inch rectangle. Transfer it to the prepared baking sheet. Spread filling over the pastry to within an inch of the edges. Evenly dot the filling with cubed butter.
Unfold the second pastry sheet; roll into a 15X10 rectangle. Place this pastry on top of the filling. Brush the edge of the bottom pastry with milk. Fold the bottom pastry over the top and gently press the edges together with a fork to seal.
Using a sharp knife, cut slits into the top pastry. Brush lightly with milk and sprinkle with coarse sugar.
Bake 50-55 minutes or until the filling is bubbly and the pastry is puffed and golden. If needed, to prevent overbrowning, cover the pie loosely with foil for the last 10-15 minutes of baking.
While the slab pie cools, prepare the butter icing. In a bowl, whisk together the confectioners’ sugar, melted butter, vanilla, and salt. Stir in enough milk to reach a drizzling consistency.
Drizzle the icing over the pastry once it’s cooled. Slice and serve.