In a saucepan over medium heat, melt 8 tablespoons of unsalted butter. Add 3 tablespoons of all-purpose flour and whisk for about 1 minute. Stir in 1 cup of granulated sugar and ¼ cup of water, continuing to whisk. Reduce the heat to low and whisk for approximately 2 minutes until the sauce thickens. Set it aside.

Peel, core, and thinly slice 6 green apples. In a large mixing bowl, combine the apple slices with 1 ½ teaspoons of ground cinnamon. Toss to coat the apples evenly. Pour the sweet butter sauce over the apple mixture and toss until all the apple slices are well coated.

Allow the store-bought pie crusts to come to room temperature for 10-15 minutes. Roll out one pie crust and place it in a pie dish. Transfer the prepared apple mixture into the pie dish. Roll out the second pie crust on a cutting board and create a lattice top or cover the pie fully, trimming and crimping the edges.

Preheat the oven to 425 degrees F. Brush the top crust with an egg wash (1 beaten egg mixed with 1 tablespoon of water). Sprinkle with sugar. Bake for 15 minutes at 425 degrees F, then reduce to 350 degrees F and bake for an additional 35-45 minutes until the crust is golden and filling is bubbly.

Let the pie cool on a wire rack for at least 2 hours to allow the filling to set. Serve with whipped cream or vanilla ice cream.