Preheat oven to 350° F. Grease and flour a Bundt pan.
In a large bowl, whisk flour, baking soda, baking powder, salt, cinnamon, and ginger.
In a stand mixer, beat butter and sugar on medium-high for 4-5 minutes until creamy, scraping down sides as necessary. Add starter and eggs. Beat on medium-high for 1-2 minutes until fluffy.
Add vanilla and mashed sweet potatoes. Beat until smooth and fold in chopped pecans and toasted pumpkin seeds.
Add the dry ingredients into the butter mixture in thirds, alternating with buttermilk. Beat on low speed until just incorporated.
Bake for 50 minutes to 1 hour, or until a toothpick inserted in center comes out clean. Gently loosen the edges with a heatproof spatula. Turn the Bundt pan onto a baking rack. After 10 minutes, remove the pan from the cake and allow the cake to cool completely.
While the cake is cooling, make the glaze. Once the cake has cooled, drizzle with glaze and top with whole pecans if desired.