For the Cake: Preheat the oven to 325 degrees F. Spray three 8-inch round cake pans with nonstick cooking spray, line the bottom of the pans with parchment paper and spray again. Set aside.
In a medium bowl, whisk together flour, baking powder, and salt. Set aside.
Using a stand mixer fitted with the paddle attachment, beat butter, oil, and sugar on medium-high speed for 3 minutes until light in color and fluffy in texture.
With the mixer on medium speed, add eggs, one at a time, scraping down the bowl between additions. Continue to beat on medium-high speed for 2 minutes until smooth. Add the vanilla and butter extract; stir to combine.
With the mixer on low speed, add in intervals, blending after each addition: 1/3 dry ingredients, 1/2 sour cream, 1/3 dry ingredients, 1/2 sour cream, 1/3 dry ingredients.
Scrape down the bowl and mix for another 20 to 30 seconds.
Divide the batter evenly among the prepared pans (18 to 19 ounces in each). Bake for 25 to 30 minutes, or until a toothpick inserted in the center of the cake comes out with a just a few moist crumbs on it.
Remove the cake pans from the oven and let the layers cool in pans for 15 minutes before inverting onto cooling racks to cool completely.
For the Chocolate Frosting: In a microwave safe bowl, heat cream for 1 minute. Pour hot cream over the chocolate chips and stir until smooth. If needed, heat the mixture for an additional 20 to 30 seconds and stir again. Cool slightly.
Using a stand mixer fitted with the paddle attachment, beat butter on medium-high speed for 3 to 5 minutes. Scrape down the bowl with a spatula.
With the mixer on medium speed, gradually add ganache to butter and mix until smooth. Scrape down the bowl and mix again for 30 seconds.
With the mixer on low speed, gradually add powdered sugar, mixing to combine after each addition. Add vanilla and salt. Stir to combine.
Turn the mixture to medium-high speed and beat for an additional 3 to 5 minutes, scraping down the bowl at least twice during the process. The buttercream should be lighter in color and silky-smooth. If the buttercream is too soft, refrigerate it for 15 to 20 minutes before using.
To Assemble the Cake: Place the first cake layer, top side up, centered on your cake board or cake plate. Evenly spread 1 cup of buttercream over the cake layer, getting eye level with the cake to ensure the buttercream is level.
Place the second cake layer, top side up, on the buttercream. Repeat previous steps.
Place the final cake layer, top side down, on the second layer of buttercream.
Spread a thin coat of buttercream around the entire cake to lock in the crumbs. Freeze for 10 to 15 minutes.
Once the crumb coat is set, frost and decorate the cake with remaining buttercream.