Step 1: Preheat your oven to 350°F (175°C) and line an 8×8 inch baking pan with parchment paper, leaving an overhang for easy removal.
Step 2: In a medium bowl, cream together the softened butter and 1/4 cup granulated sugar. Gradually add the flour and salt, mixing until a crumbly dough forms.
Step 3: Press the dough firmly into the bottom of the prepared pan and bake for 12-15 minutes until the edges are very lightly golden.
Step 4: While the crust is baking, whisk together the sweet potato puree, eggs, 1/2 cup brown sugar, heavy cream, vanilla, cinnamon, ginger, and nutmeg in a large bowl until smooth.
Step 5: Pour the sweet potato filling over the pre-baked crust and smooth the top with a spatula.
Step 6: In a small bowl, toss the chopped pecans with 2 tablespoons of melted butter and 1/4 cup of brown sugar until evenly coated.
Step 7: Sprinkle the pecan mixture evenly over the sweet potato layer.
Step 8: Bake for 30-35 minutes, or until the filling is set and no longer jiggles in the center.
Step 9: Remove from the oven and allow to cool completely in the pan on a wire rack. Refrigerate for at least 4 hours before slicing into squares.