Sunday's Texas Sheet Cake

Ingredients

• 2 sticks butter, cut into cubes
• 1 cup water
• 2 cups all-purpose flour
• 2 cups granulated sugar
• 2 eggs, beaten
• 1/2 cup sour cream
• 1 teaspoon vanilla bean paste or vanilla extract
• 1 teaspoon salt
• 1 teaspoon baking soda
• 1/2 cup butter
• 1/4 cup milk
• 4 cups powdered sugar
• 1/2 teaspoon vanilla bean paste or vanilla extract
• 1 cup walnuts, chopped