Working ahead of time, roast the sweet potatoes. Preheat oven to 350 degrees F. Poke sweet potatoes all over with the tines of a fork and wrap tightly with foil. Set in a baking dish and roast 60 - 70 minutes, or until sweet potatoes are soft and yielding. Set aside to cool. Sweet potatoes can be roasted ahead of time and kept in the fridge for up to 3 days.

Preheat oven to 350 degrees F. Butter a 9-inch pie pan and set aside.

To make the crust, pulse to reduce graham crackers in the bowl of a food processor. Add sugar and sea salt and pulse to combine. Drizzle in butter and pulse 2 - 3 times. Using a flat-bottomed glass or measuring cup, press graham mixture into pie pan, keeping the crust at an even thickness. Gently set on a rimmed baking sheet and bake 10 minutes. Set aside to cool.

Wipe food processor clean. Trim fibrous ends from cooked sweet potatoes and discard. Cut sweet potatoes down the middle and scoop out the soft flesh, leaving skin behind. Set sweet potato flesh in food processor and process until smooth, stopping to wipe down sides as needed.

In a large mixing bowl, whisk to combine eggs, cream, brown sugar, spices and sea salt. Fold in sweet potato puree, vanilla, and bourbon. Lastly, drizzle in the butter and stir until combine. Spoon filling into pre-baked crust. Smooth out the top as best you can. Bake until a stainless knife inserted in the center comes out with just a few streaks, 60 - 70 minutes.

Set on a wire rack and cool 3 hours or more. Once cool, pie can be loosely covered and refrigerated several hours or overnight.

To serve, combine cream, brown sugar, and sea salt, and whip to soft peaks. Serve pie with whipped cream and a pinch of nutmeg.