Smith Island Cake

Preparation

1. Cake

   Step 1

   Place racks in upper and lower thirds of oven; preheat to 350°. Lightly coat four 9"-diameter cake pans (or as many as you have) with nonstick vegetable oil spray and line the bottom of each with a parchment paper round. Whisk 4⅔ cups (583 g) all-purpose flour, 1 Tbsp. plus 1 tsp. baking powder, and 1 Tbsp. Diamond Crystal or 1¾ tsp. Morton kosher salt in a large bowl to combine.

   Step 2

   Beat 4 cups (800 g) granulated sugar, 1 cup plus 5 Tbsp. unsalted butter, room temperature, and 1 Tbsp. vanilla extract in the bowl of a stand mixer fitted with the paddle attachment, starting on low speed to keep sugar from flying out of the bowl and working up to high, until light and fluffy, about 3 minutes. Reduce speed to medium and, with motor running, add 8 large eggs, room temperature, one at a time, incorporating completely after each addition, about 2 minutes total. Reduce speed to low and, with motor running, gradually add about a quarter of dry ingredients and about ½ cup of 2 cups milk, room temperature; beat just until combined, about 30 seconds. Repeat in 3 more batches, mixing until no lumps of dry flour remain after the final addition, about 3 minutes total.

   Step 3

   Add about 3 cups (615 g) batter to each prepared pan. Bake, placing 2 pans on each rack and rotating top to bottom and front to back halfway through, until a tester inserted into the center comes out clean and edges are starting to pull away from sides of pans, 30–40 minutes. Transfer pans to wire racks and let cakes cool in pans 10 minutes. Run an offset spatula around inside of pan to loosen cakes and turn out onto racks. Let cakes cool completely. (If you don’t have 4 pans, bake 2 cakes, then let pans cool slightly, before cleaning and preparing again with more nonstick spray and fresh parchment paper rounds.)

2. Frosting and Assembly

   Step 4

   Bring 2⅔ cups heavy cream, ½ cup light corn syrup, 1 Tbsp. vanilla extract, and 1¾ tsp. Diamond Crystal or 1 tsp. Morton kosher salt to a simmer in a medium saucepan over medium heat. Add 18 oz. bittersweet chocolate, chopped and immediately remove pan from heat. Let sit 5 minutes. Whisk frosting until smooth. Let cool until very thick, like pudding, but still pourable, 30–45 minutes.

   Step 5

   Using a long serrated knife, slice each cake in half horizontally to create eight layers total. Place a cake layer, cut side down, on a wire rack set inside a parchment-lined rimmed baking sheet. Spread ⅓ cup frosting over cake in a thin, smooth layer. Place another cake layer, cut side down, on top and spread another ⅓ cup frosting over. Repeat process 5 more times, then place final cake layer on top. Spread about 1 cup frosting over top and sides of cake to create a thin coat to lock in any crumbs. Chill until frosting is set and mostly firm to the touch, about 15 minutes.

   Step 6

   Reheat remaining frosting over low, stirring constantly, just until thin and pourable. (You want it to be as loose as you can make it.) Remove cake from fridge and pour remaining frosting over, allowing it to evenly drip down the sides. Using an offset spatula and working quickly, cover any spots where melted frosting did not coat. Chill cake 15 minutes to let frosting set. Transfer cake to a cake platter or large plate with 2 very large, thin spatulas.