Preheat the oven to 350°F.
Combine graham cracker crumbs, pecans, and brown sugar in a large bowl. Add melted butter, mixing until crumbs are evenly moistened. Press into a 9-inch pie plate.
1 1/2 cups crushed graham cracker crumbs, 1/2 cup finely chopped pecans, 2 Tablespoons brown sugar, 1/4 cup salted butter
Bake the crust for 8-10 minutes to set. Remove from the oven and cool completely.
In a medium saucepan over medium heat, mix brown sugar, corn syrup, water, butter, and salt together until butter is melted.
1 1/2 cups light brown sugar, 2/3 cup light corn syrup, 1/3 cup water, 1/4 cup salted butter, 1/8 teaspoon salt
Bring mixture to a boil, do not stir, and let it cook until it reaches 236°F (soft ball stage).
Remove from heat and stir in evaporated milk and vanilla. Pour into a heatproof jar and set aside to cool completely.
2/3 cup evaporated milk, 1 teaspoon pure vanilla extract
Melt butter in a small skillet over medium heat. Add chopped pecans and toast for 3-5 minutes until fragrant. Remove from heat and cool completely.
2 Tablespoons salted butter, 1/2 cup roughly chopped pecans
Spoon half of the ice cream into the cooled crust. Drizzle with 1/4 cup of butterscotch sauce. Sprinkle with half of buttered pecans. Spoon remaining ice cream on top and press into an even layer.
1 1/2 quarts butter pecan ice cream
Cover with plastic wrap and freeze for 12 hours.
Remove plastic wrap and drizzle with additional 1/4 cup of butterscotch sauce. Sprinkle with remaining buttered pecans.
Let the pie stand for 5 minutes to soften slightly before slicing and serving. There will be more butterscotch sauce than needed for the pie itself. Leftovers can be stored in the refrigerator for up to 1 month.