Preheat the oven to 350°F. Lightly spritz a 9-inch deep dish pie pan with cooking spray. Press the pie crust firmly into the pie pan. Prick the bottom of the pie crust with a fork. Place onto a baking sheet and into the oven to bake for 7 minutes. Set aside.
In a medium mixing bowl, whisk together sweet potato puree, cream, granulated sugar, brown sugar, eggs, pumpkin pie spice, vanilla and salt . Mix until fully combined.
Pour custard into crust. Place into the oven and bake for 30 minutes.
Meanwhile, in a small mixing bowl, mix together vanilla wafer crumbs, granulated sugar and cinnamon. Cut butter into the mixture using a pastry blender or two forks until it resembles coarse crumbs. Mix-in the chopped pecans and English toffee bits by hand.
After baking for 30 minutes, sprinkle the pecan-crunch streusel over the top of the custard. Continue to bake for an additional 30 minutes until the custard is set when gently shaken and the pecan-crunch streusel is golden. Cover the edge of the crust with aluminum foil to prevent over-browning, if needed.
Cool the pie to room temperature then chill completely before cutting. Overnight is ideal. Serve with a dollop of fresh whipped cream, if desired.