Adapted by Rebecca Minkoff from Ina Garten for Barefoot Contessa.
18 Tbsp. (2¼ sticks) unsalted butter, at room temperature
3 cups sugar
6 extra-large eggs
1 cup sour cream
1½ tsp. pure vanilla extract
1 lemon, zested
3 cups all-purpose flour
1/3 cup cornstarch 1 tsp. kosher salt
1 tsp. backing soda P
reheat oven to 350°F. Butter and flour a 12-by-18-by-1½-inch sheet pan.
Cream butter and sugar on medium-high speed in bowl of a stand mixer until light and fluffy, about 5 minutes. On medium speed, add eggs, 2 at a time, then sour cream, vanilla, and lemon zest. Mix well. Sift together flour, cornstarch, salt, and baking soda. With mixer on low speed, slowly add flour mixture to butter mixture and stir just until smooth. Finish mixing by hand to be sure batter is well mixed. Pour evenly into pan, smooth top with a spatula, and bake in center of oven for 25 to 30 minutes, or until a toothpick comes out clean. Cool in pan to room temperature.
24 oz. semisweet chocolate chips
1½ cups heavy cream
2 Tbsp. light corn syrup
½ tsp. pure vanilla extract
4 Tbsp. (½ stick) unsalted butter, at room temperature
Chocolate candies for decorating
Place chocolate chips and heavy cream in a bowl set over a pot of simmering water, stirring occasionally, until chips are completely melted. Off heat, add corn syrup and vanilla and allow chocolate mixture to cool to room temperature. In bowl of a stand mixer fitted with whisk attachment, whisk chocolate mixture and softened butter on medium speed for a few minutes, until it’s thickened. Spread frosting evenly on cake and decorate.
( via here )