Yellow Layer Cake with Chocolate-Sour Cream Frosting

INGREDIENTS

• 14 ounces semisweet or bittersweet chocolate, chopped
• 2 cups sugar
• 4 cups cake flour
• 1 1/2 teaspoons baking soda
• 2 cups sour cream
• 1/4 cup light corn syrup
• 6 large egg yolks
• 2 teaspoons baking powder
• 1/2 cup (packed) light brown sugar
• 1/2 cup vegetable oil
• 2 3/4 cups powdered sugar
• 1 1/2 teaspoons vanilla extract
• 3/4 cup (1 1/2 sticks) unsalted butter, room temperature
• 1 cup (2 sticks) unsalted butter, room temperature
• 1 vanilla bean, split lengthwise
• 1 1/2 cups buttermilk
• 3 large eggs
• Nonstick vegetable oil spray
• 1 1/2 teaspoons kosher salt
• 2 teaspoons vanilla extract