Step 1: Preheat your oven to 350°F (175°C) and line a 9x9 inch baking pan with parchment paper, leaving an overhang on the sides for easy removal.
Step 2: In a large bowl, cream together 1 cup of softened butter and 1/2 cup of granulated sugar until light and fluffy. Gradually stir in the flour and salt until a crumbly dough forms.
Step 3: Press the dough firmly into the bottom of the prepared pan. Bake for 15-18 minutes or until the edges are just beginning to turn golden. Remove from the oven and let cool slightly.
Step 4: In a separate bowl, whisk together the mashed sweet potato puree, eggs, 1/2 cup brown sugar, heavy cream, vanilla, cinnamon, ginger, and nutmeg until completely smooth.
Step 5: Pour the sweet potato mixture over the pre-baked crust and spread it evenly with a spatula.
Step 6: In a small bowl, toss the pecan halves with 2 tablespoons of melted butter and 1/4 cup of brown sugar. Sprinkle the pecans evenly over the sweet potato layer.
Step 7: Bake for an additional 30-35 minutes, or until the filling is set and the pecans are golden brown. Let the bars cool completely in the pan on a wire rack before slicing into 16 squares.