Bring a large pot of salted water to a boil. Add the sweet potatoes and cook for about 15-20 minutes, or until fork tender. Drain and mash until smooth, using 2 1/2 cups for this recipe. Set aside to cool.

Preheat your oven to 350°F (175°C) and spray a 10-inch Bundt pan with nonstick cooking spray.

In a stand mixer, cream the sugar and softened butter on medium speed until light and fluffy, about 3-4 minutes.

Mix in the mashed sweet potatoes and vanilla extract until well blended.

Add the eggs one at a time, beating well after each addition.

In a separate bowl, whisk together the flour, baking powder, cinnamon, baking soda, nutmeg, allspice, and salt. Gradually add this to the sweet potato mixture on low speed until just combined.

Pour the batter into the prepared Bundt pan and smooth the top.

Bake for 55-60 minutes, or until a toothpick comes out clean when inserted into the center.

Let cool in the pan for about 20 minutes, then invert onto a serving plate and cool completely.

Melt the remaining butter in a small saucepan. Stir in maple syrup and heavy cream, bringing it to a gentle boil for 1 minute. Remove from heat and whisk in confectioners' sugar until smooth. Allow to cool slightly until it thickens.

Drizzle the glaze over the cooled cake and sprinkle with pecans, if using.