Instructions

• Preheat the oven to 325°F (163°C). Spray three 8-inch round cake pans with nonstick cooking spray, line the bottoms with parchment paper, and spray the parchment; set the pans aside.
• In a medium bowl, whisk together 3 cups (345 g) cake flour, 2 teaspoons (8 g) baking powder, and 1 teaspoon (6 g) salt; set aside.
• In the bowl of a stand mixer fitted with the paddle attachment, combine 1 cup (226 g) unsalted butter (room temperature), 1/3 cup (72 g) grapeseed oil, and 1 3/4 cups (350 g) granulated sugar. Beat on medium-high speed for 3 minutes, until the mixture is light in color and fluffy.
• With the mixer on medium speed, add the 5 large eggs, one at a time, scraping down the bowl between each addition. After the last egg, add the 2 egg yolks and continue to beat on medium-high speed for 2 minutes, until smooth.
• Add 1 teaspoon (4.2 g) pure vanilla extract and 1 teaspoon (4.2 g) butter extract to the batter and mix briefly to combine.
• Reduce the mixer speed to low. Add the dry ingredients and 1 cup (240 g) sour cream in this order, in intervals, mixing briefly after each addition: one-third of the dry mix, half of the sour cream (1/2 cup), one-third of the dry mix, the remaining half of the sour cream (1/2 cup), then the final one-third of the dry mix. Scrape down the bowl and mix 20 to 30 seconds more to ensure everything is combined.
• Divide the batter evenly among the three prepared pans. Bake the layers for 25 to 30 minutes, or until a toothpick inserted in the centers comes out with just a few moist crumbs attached.
• Remove the pans from the oven and let the layers cool in the pans for 15 minutes. Then invert the layers onto cooling racks and allow them to cool completely.
• While the cakes are cooling, make the chocolate ganache: place 1 cup (170 g) semi-sweet or dark chocolate chips in a microwave-safe bowl. Heat 1/4 cup (57.75 g) heavy whipping cream in the microwave until hot (do not boil), pour the hot cream over the chocolate chips, and stir until the chocolate is fully melted and the mixture is smooth. If needed, heat briefly in additional 20–30 second bursts to finish melting. Set the ganache aside to cool slightly until warm and pourable.
• Sift the 5 cups (625 g) confectioner's sugar and have it ready to add to the butter.
• Prepare the buttercream: in the stand mixer fitted with the paddle attachment, beat 2 cups (452 g) unsalted butter (slightly cold) on medium-high speed for 3 to 5 minutes. Scrape down the bowl.
• With the mixer on medium speed, gradually add the warm ganache to the butter and mix until smooth. Scrape down the bowl.
• With the mixer on low speed, gradually add the sifted confectioner's sugar, mixing briefly to combine after each addition. Add 1 tablespoon (12 g) pure vanilla extract and a pinch of salt. Mix to combine.
• Increase the mixer to medium-high speed and beat the buttercream for an additional 3 to 5 minutes, scraping down the bowl at least twice during this time. The buttercream should be lighter in color and silky-smooth. If the buttercream is too soft to spread, refrigerate it for 15 to 20 minutes, then re-whip briefly to restore spreadability.
• Assemble the cake: place the first cake layer, top side up, centered on your cake board or serving plate.
• Evenly spread 1 cup of the buttercream over the first layer, checking at eye level to ensure the layer of buttercream is level.
• Place the second cake layer, top side up, on top of the buttercream. Evenly spread 1 cup of buttercream over the second layer.
• Place the final cake layer, top side down, onto the second layer of buttercream (this helps create a flat top).
• Apply a thin coat of buttercream around the entire cake to lock in crumbs (the crumb coat). Smooth as needed, then place the cake in the freezer for 10 to 15 minutes to set the crumb coat.
• Once the crumb coat is set, use the remaining buttercream to frost and decorate the cake as desired.