Good-Cooking - Chocolate Skillet Cake

Ingredients

• 1/2 cup butter
• 1 cup granulated sugar
• 2 eggs
• 1 cup light Karo syrup (see note)
• 1 teaspoon vanilla extract (optional)
• 1 3/4 cups all-purpose flour
• 1/3 cup cocoa
• 1 teaspoon baking soda
• 1 teaspoon baking powder
• 1 teaspoon cinnamon (optional)
• 1 cup sour milk (see note)