Preheat oven to 350 degrees. Spray a standard 12-cup muffin pan with nonstick cooking spray; set aside.
Beat butter and sugar on medium speed in the bowl of an electric mixer fitted with a paddle attachment until smooth. Add eggs, one at a time, and beat to combine.
In a medium bowl, combine flour and baking soda. Gradually add half the flour mixture to the butter mixture, beating on low speed until blended, scraping the bottom and down sides of bowl with a rubber spatula, as needed. Add remaining flour mixture, and beat until blended. Add vanilla, salt, ginger, cinnamon, sweet potatoes, and buttermilk. Beat on medium speed until smooth.
Spoon batter into prepared muffin pan. Each cup should be about two-thirds full. Bake until a wooden toothpick inserted into the center of each cake comes out clean, about 15 minutes. Transfer pan to wire rack to cool for 5 minutes. Remove warm cakes from pan, and sprinkle with toasted pecans. Top each cake with 2 1/2 tablespoon caramel-pecan sauce. Serve with vanilla ice cream, if desired.