*Plan ahead for this cake since you have to let the starter sit for 2-3 hours before baking.*

Prepare the starter:

• Mix the starter, warm milk and flour in a mixing bowl. Cover and allow this mixture to sit for about 2-3 hours. It is ready to use when it starts smelling yeasty and slightly like sour milk.

Mix the cake:

• Cream together the sugar, vanilla, baking soda, salt, butter and cinnamon until well creamed. Scrape the sides of the bowl as needed.
• Add the eggs, one at a time, beating between each addition.
• Stir in the melted chocolate.
• Add this mixture into the sourdough mixture.
• Use a rubber spatula to mix the ingredients together initially.
• Use hand mixer to continue mixing until the sourdough until completely combined. The sourdough will be sticky and stretchy, so it can be difficult to get fully mixed. But if you don't make sure it is mixed, the cakes will not bake evenly. Beat for at least 1 minute on low speed, scraping the sides of the bowl as needed.
• Preheat the oven to 350º Fahrenheit. Grease with shortening and flour two 9" round cake pans. (or rub with cake release)
• Spoon the batter evenly between the two cake pans.
• Bake for 25-30 minutes or until the cake tests done (toothpick inserted in the center comes out clean).
• Place one cake on a large cake plate. Top with 3/4 cup frosting and spread to the edges.
• Place the second cake on top. Then frost the top and outsides of the cake.
• If you choose to put sprinkles or other toppings on the cake, be sure to do that before the frosting crusts over.
• Store at room temperature in an airtight container.