Preheat oven to 350°F (175°C). Grease and flour a 10-inch Bundt pan.

In a large bowl, cream together the softened butter and granulated sugar until light and fluffy.

Beat in the mashed sweet potato and vanilla extract until well combined.

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 the dry ingredients to the wet ingredients, mixing on low speed until just combined. Do not overmix.

Pour the batter evenly into the prepared Bundt pan, smoothing the top.

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

Let the cake cool in the pan for 20 minutes before inverting it onto a wire rack to cool completely.

While the cake is cooling, prepare the glaze. In a small saucepan over medium heat, melt the butter.

Stir in the maple syrup and heavy whipping cream.

Bring the mixture to a gentle boil and cook for 1 minute.

Remove from heat and whisk in the sifted confectioners' sugar until smooth and slightly thickened.

Let the glaze cool for about 25-30 minutes, or until it thickens enough to coat the back of a spoon.

Drizzle the cooled glaze over the completely cooled cake. Sprinkle with chopped pecans, if desired.