Preheat oven to 375ºF. Using a fork, toss the cookie crumbs, brown sugar, and melted butter together in a medium bowl. Press mixture into the bottom and sides of a 9-inch pie dish; set aside.

In a medium saucepan, melt the butter over medium-low heat. As the butter melts, it’ll start to foam, then turn a clear golden color. Continue to stir the butter, scraping up any browned specks from the bottom of the pan as it starts to brown. It should have a nutty aroma. Once browned and nutty, remove from the heat and add the puréed sweet potato, both sugars, spices, salt, and about half of the evaporated milk, whisking until smooth. Add the eggs, one at a time, followed by the rest of the evaporated milk and vanilla.

Pour sweet potato filling into the crust** and bake in the oven for 55-60 minutes, or until filling is set around the edges and center jiggles only slightly. If the pie is browning quicker than you’d like it to, cover it with a piece of foil to slow down the browning process.

When the pie is done baking, remove it from the oven and allow it to cool completely--about 2 hours.

Add the egg whites*** and sugar to a large heatproof bowl and set over a saucepan of barely simmering water. Heat mixture, stirring constantly, until it the temperature hits 160ºF on a candy thermometer, about 3 – 5 minutes. Remove bowl from saucepan, add the cream of tartar, and beat mixture with an electric hand-mixer (or in a stand mixer) on high speed until stiff glossy peaks form, about 6 – 8 minutes. Add the vanilla near the very end. Spread on top of the cooled pie.

Toast the topping with a kitchen torch, or under the broiler of your oven. Cut into slices and serve.