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Summer Dempsey

Sourdough Discard Chocolate Cake

A rich, moist sourdough discard chocolate cake with silky chocolate buttercream. Made in two bowls with no mixer for the cake — the hot water trick blooms the cocoa for the deepest possible chocolate flavor, and the discard keeps the crumb tender for days. Perfect for birthdays, potlucks, or any time you've got discard to use up.
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Prep Time 15 minutes
Cook Time 30 minutes
Cooling time 30 minutes
Total Time 1 hour 15 minutes
Servings: 12 -15 people
Course: Dessert
Cuisine: American
Calories: 420

Ingredients
  

Wet Cake Ingredients
  • 1 cup sourdough discard
  • 1 cup milk or buttermilk
  • ½ cup vegetable oil
  • 2 large eggs
  • 1 teaspoon vanilla extract
  • 1 cup hot water (added very last)
Dry Cake Ingredients
  • 2 cups granulated sugar
  • 1¾ cups all-purpose flour
  • ¾ cup cocoa powder
  • 1½ teaspoons baking soda
  • 1 teaspoon baking powder
  • 1 teaspoon salt
Frosting
  • ¾ cups unsalted butter (1½ sticks) softened
  • ½ cup unsweetened cocoa powder
  • 2½ –3 cups powdered sugar
  • ¼ cup heavy cream or milk
  • 1 teaspoons vanilla extract
  • ⅛ teaspoon salt

Method
 

  1. Preheat your oven to 350°F. Grease a 9×13 baking pan or two 8-inch round cake pans and set aside.
  2. In a large bowl, whisk together the sugar, flour, cocoa powder, baking soda, baking powder, and salt until evenly combined.
  3. In a separate bowl, whisk the sourdough discard, milk (or buttermilk), oil, eggs, and vanilla extract- making sure to mix well. (making sure eggs are room temp as well as discard)
  4. Pour the dry ingredients into the bowl with the wet ingredients and mix just until combined. Slowly add the hot water, stirring until the batter is smooth. The batter will be fairly thin, which is exactly what you want for a moist cake.
  5. Pour the batter into the prepared pan and bake for 30–35 minutes, or until a toothpick inserted into the center comes out clean. Allow the cake to cool completely before frosting.
  6. While the cake is cooling, place the softened butter in a large mixing bowl. Beat with a mixer for 2–3 minutes until light and creamy.
  7. Mix in the cocoa powder until fully combined with the butter.
  8. Gradually add the powdered sugar, mixing on low speed so it blends smoothly into the frosting.
  9. Add the heavy cream, vanilla extract, and salt. Beat the frosting for another 2–3 minutes until it becomes light, fluffy, and easy to spread. If it feels too thick, add a small splash of cream. If it’s too soft, mix in a little more powdered sugar.
  10. Once the cake is completely cool, spread the chocolate buttercream evenly over the top.Slice and serve.

Notes

Use room-temperature ingredients. Cold eggs and cold discard from the fridge can cause the batter to seize. Let them sit on the counter for 20–30 minutes before mixing, or warm cold eggs in a bowl of warm water for 5 minutes.
Spoon and level your flour. Packed flour is the #1 cause of dry chocolate cake.
The water must be HOT. Not lukewarm. Hot water blooms the cocoa and creates the moist, tender crumb. Don't skip or shortcut this step.
The batter will be thin. Don't try to thicken it — that's exactly how it should be. Thin batter = moist cake.
Don't overmix. Once wet meets dry, stir just until combined. Overmixing develops gluten and gives you a tough cake.
Test early. Start checking at 28 minutes for a 9×13 and 25 minutes for round pans. The line between perfectly moist and dry is just a few minutes.
Cool completely before frosting. Warm cake melts buttercream. If you're in a hurry, 30 minutes in the fridge speeds it up.
Coffee swap. Substitute hot brewed coffee for the hot water for an even deeper chocolate flavor — it doesn't make the cake taste like coffee.
Storage. Covered at room temperature for 2 days, refrigerated for up to 5 days. Freezes beautifully (frosted or unfrosted) for up to 2 months.