Make the Gingersnap Crust

1. Preheat the oven to 375 degrees F. 
2. Crumb the gingersnaps finely in a food processor or blender
3. In a mixing bowl, mix together crumbs and brown sugar.
4. Pour the melted butter over the crumb mixture and mix until well coated.
5. Press the mixture into a pie or tart pan until firmly and evenly packed on the bottom and sides. You can press another pie or tart pan over the crust to make it even and uniform.
6. Bake until golden, 10 to 15 minutes. Remove from the oven and cool.

Make the sweet potato filling:

1. Preheat the oven to 400 degrees F. 
2. Place sweet potatoes on a foil-lined baking sheet and bake until very soft, about 1 hour. 
3. When potatoes are cool enough to handle, halve and scoop out enough flesh to measure 2 cups.
4. While potatoes are still hot, add butter and mash until almost smooth; small lumps of potato should remain.
5. Whisk together eggs, sugar, spices and salt. Stir in heavy cream, lemon juice, and vanilla. Gradually add egg mixture to sweet potatoes, whisking gently to combine. 
6. Pour the filling into the cooled piecrust. Bake for 20 minutes. Reduce the heat to 325 degrees F and bake until the filling is set around edges but still jiggles slightly when shaken, about 20 more minutes. Remove from the oven and let cool slightly, about 30 minutes. 

Make the Meringue Topping:

1. To make the meringue topping, in a large bowl, beat the egg whites until soft peaks start to form. Slowly add the sugar while beating constantly. Beat until glossy and stiff peaks form, being careful not to over beat the meringue. 
2. Preheat the broiler
3. While the pie is still warm, spread the meringue evenly over the filling, smoothing out to the pastry edges to seal. 
4. Place under the broiler and cook until the meringue is golden brown, about 1 minute. 
5. Remove from the oven and let cool completely on a rack, about 1 hour