Place the oil, brown sugar, granulated sugar, and vanilla in a stand mixer bowl or large mixing bowl and mix or whisk to combine.

Add the eggs and yolks one at a time, mixing after each addition. Add the pumpkin puree and mix until blended.

Put a sheet of parchment paper or a large plate on a work surface and sift the flours, baking powder, baking soda, salt, and spices onto it. Use the paper to pour dry ingredients into wet in three additions, mixing them into the batter until just blended. Do not overmix.

Thoroughly scrape batter into the prepared pan and smooth the top with a spatula.

Bake the cake on middle rack of oven for 20 minutes.

Rotate pan and continue baking until a toothpick inserted in center of cake comes out with a moist crumb or two, 15-20 minutes.

Check to see that cake is done. Remove from oven or add time as needed.

Let the cake rest on a cooling rack until cool enough to handle, about 30 minutes. Invert onto a serving platter or baking sheet to cool completely. Meanwhile, make the frosting.

Place the butter in the stand mixer bowl. Mix on medium speed until smooth, scraping down the bowl as needed.

Put a sheet of parchment or a large plate on a work surface and sift the sugar, salt, and cocoa powder onto it. Use the paper to pour dry ingredients into the butter a little at a time, mixing on low speed to incorporate between each addition.

Add the bourbon and cream, beating on medium speed and scraping down the bowl as needed. Add the vanilla and beat on medium speed until frosting is light and fluffy, 3-5 minutes. Cover the bowl and set frosting aside until cake is cool.

Tuck strips of parchment paper or waxed paper under the cake to keep platter clean while you frost. Generously spread cake with frosting, leaving sides bare if you like. Carefully pull out the strips of parchment.

Cut the cake into slices and serve. Store leftovers at room temperature loosely wrapped in plastic wrap or draped in parchment paper for up to three days.