Texas Sheet Cake

INGREDIENTS

• 1/4 cup (1 ounce) lightly packed premium unsweetened cocoa, preferably Dutch-processed
• 2 cups (14 ounces) sugar
• 2 cups (10 ounces) all-purpose flour
• 2 teaspoons pure vanilla extract
• 2 eggs
• 1 cup water
• 1 cup (8 ounces) unsalted butter
• 3 tablespoons canola oil
• 1/2 cup (2 1/8 ounces) toasted chopped nuts (such as walnuts, pecans, or hazelnuts)
• 1 teaspoon baking soda
• 1/2 teaspoon fine sea salt
• 1/3 cup whole milk
• 1/2 cup (4 ounces) unsalted butter
• 1/2 cup buttermilk
• 1/2 cup (1 3/4 ounces) lightly packed premium unsweetened natural cocoa
• 3 cups (12 ounces) sifted confectioners' sugar