Cook sweet potatoes in a pot of boiling water, stirring occasionally, until a tester inserted into centers with no resistance, 40-45 minutes. Drain and let cool enough to handle. Remove skins, transfer flesh to a medium bowl, and mash. Let cool.
Preheat the oven to 350°F.
Line bottoms of three 9” cake pans with parchment paper, then spray with Baker's Joy.
Sift cake flour, baking powder, baking soda, cinnamon, nutmeg, ginger and salt into a large bowl.
Combine granulated sugar, brown sugar, butter, oil, and vanilla in the bowl of a stand mixer fitted with the paddle attachment. Beat on medium-high speed until light and fluffy, and no lumps remain, about 5 minutes.
Add eggs to sweet potato mash and whisk until combined. Scrape into the sugar mixture and beat to combine, scraping down the bowl as needed.
Reduce speed to low and gradually add flour mixture, and alternate each addition with buttermilk. Mix until just incorporated.
Divide batter evenly among prepared pans. Bake 25-30 minutes, until cakes are slightly risen, tops are set, and a tester inserted into the centers comes out clean.
Transfer pans to a wire rack and let cakes cool in pans for 10 minutes. Turn cakes out onto racks. Remove parchment paper if on the cake, and let cool completely.
Tightly wrap cakes individually in plastic wrap and place in the freezer until chilled, about 2 hours. This makes for easier frosting.
Cream the butter and cream cheese in the bowl of a stand mixer for 3 minutes. At the end of 3 minutes, scrape the bowl.
Add the vanilla extract, cinnamon, and salt, and beat for 1-2 minutes.
Slowly add the confectioners’ sugar, beating on low to ensure the sugar does not fly out of the mixing bowl. After each addition, scrape the bowl.
Once all the confectioners’ sugar is incorporated, beat on low speed for 3 minutes.
Spread icing between cake layers and then on the top and sides of the stacked layers. I love using the Kitty Swirl!
Chill to set the icing and serve at room temperature.