6cups(750 g) powdered sugarmeasured and then sifted
1 teaspoon(4.2 g) vanilla extract
1/4cup(57.75 g) heavy whipping cream
Pinch of salt
4 tbsp.(58 g) strained juice from cranberry compote
*This buttercream recipe makes enough to fill and cover your cake. If you want to add additional piping, you’ll want to make an extra 1/2 batch.
For the Cake
Preheat your oven to 350 degrees F. Spray three 8- inch or four 6-inch pans with nonstick spray, line the bottoms with parchment paper and spray again. Set aside.
In a medium size bowl, combine the egg whites, whole eggs, and vanilla. Set aside.
In another mixing bowl, combine the cake flour, pistachios, baking powder, salt, lime zest and Jell-O mix. Stir with a whisk and then set aside.
In a bowl of an electric mixer fitted with a paddle attachment, beat the butter and the sugar until light and fluffy, about two minutes.
Add the egg mixture in a few additions, making sure to scrape down the sides and bottom of the bowl between each one. Beat until well blended, about one minute.
With your mixer on low speed, alternately add the flour mixture and the buttermilk, starting and finishing with the flour mixture. Between each addition, you're only mixing for about 10-20 seconds. Once all of the flour mixture and buttermilk are added, keep your mixer on low speed and mix until the ingredients are incorporated. This should only be about 30 seconds or so. Make sure to scrape down the bottom and sides of the bowl and mix again for just 10 to 20 seconds. Over mixing your batter will cause it to sink, not rise, or taste dense.
Divide batter evenly among your prepared pans, about 16 oz of batter in each for the 8-inch pans or 12 oz in the 6-inch pans.
Bake the cakes for about 22 to 25 minutes, or until a toothpick comes out with a few crumbs on it. Let cool on wire racks for 10 minutes before inverting them onto cooling racks to cool completely.
After the cakes are cooled completely, level the tops, if needed. You'll then wrap each cake layer in plastic wrap and freeze for at least an hour before decorating. It's important to use slightly-chilled cakes when you decorate. The colder cakes will make it easier to handle and you'll have less crumbs get into your crumb coat.
If you're making the cakes several days ahead of time, you'll freeze the layers and then give them about 30 to 60 minutes to thaw before decorating.
For the Cranberry Compote
In a saucepan, combine the cranberries, sugar and water over medium heat. Stir to dissolve the sugar and then cover to allow the cranberries to cook and soften.
When the cranberries have softened and begin to pop, slowly add the sifted corn starch and stir until it is incorporated. (If you don't sift the cornstarch, you'll likely get white clumps in the compote that are hard to dissolve).
Allow the cranberries to simmer for another 5-10 minutes. The mixture will become thick and somewhat jelly-like. Transfer to a heatproof bowl and let cool to room temperature or store, covered, in the refrigerator until ready to use.
For the Buttercream
In a stand mixer fitted with a paddle attachment, cream the butter on medium-high speed for about two minutes.
With the mixer on low speed, gradually add the sifted powdered sugar until incorporated. Scrape down the sides of the bowl and continue to mix for another minute.
Slowly add the heavy cream, followed by the vanilla, pinch of salt and strained cranberry sauce. Once incorporated, turn the speed to medium-high and beat the frosting for 3 to 5 minutes.
Be sure to mix the frosting by hand with a spatula or wooden spoon before apply your final coat of frosting. This will help push out the air pockets and create a silky, smooth buttercream which will be easier for you to smooth.
Spread a little dollop of frosting on a cake board or cake plate to hold your cake in place. Place your first cake layer, top side up, in the center of the cake board.
Evenly spread about 3/4 cup frosting over the cake and then pipe a small rim of frosting around the edge of the cake to create a barrier for the cranberry compote.
Fill the center of the cake with about 1/2 to 3/4 cup compote. You don't want to over fill the center so the compote doesn't spill out the sides. Reserve any left over compote and serve a scoop of it with the slice of each cake.
Follow these steps for the next cake layer and filling.
Place the final cake layer, top side down, on the last layer of filling.
Apply a thin layer of frosting around the entire cake. This is your crumb coat, which will lock in your crumbs. Freeze the cake for 10 to 15 minutes.
Once the crumb coat is set, finish frosting the cake with the remaining buttercream.
Use fresh cranberries and pistachios for decorating.
If you want to pipe additional decorations on or around your cake, I suggest making an extra half batch of my frosting.