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A slice of sourdough marble cake with swirls of chocolate and vanilla sits on parchment paper next to a silver fork, with more slices of cake in the background.

Sourdough Marble Cake

Elien Lewis
A tender sourdough marble loaf cake with swirls of vanilla and bloomed chocolate batter. The batter can be baked straight away or fermented overnight for a softer crumb and deeper flavour.
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Prep Time 20 minutes
Cook Time 1 hour
Total Time 1 hour 20 minutes
Course Dessert, Snack
Cuisine American
Servings 10 slices
Calories 301 kcal

Ingredients
 
 

Cake batter

  • 115 g unsalted butter softened
  • 30 g vegetable oil
  • 200 g granulated sugar
  • 3 large eggs room temperature
  • 1 tsp vanilla paste or extract
  • 100 g sourdough discard room temperature
  • 120 g natural yoghurt room temperature
  • 220 g all-purpose flour
  • 1 tsp baking powder
  • 1/2 tsp baking soda
  • 1/2 tsp salt
  • 80 g whole milk room temperature

Chocolate swirl

  • 30 g whole milk hot
  • 25 g cocoa powder
  • 25 g granulated sugar
  • 1 tsp instant espresso powder optional

Instructions
 

  • Grease and line a 9x5 inch (23x13cm) loaf pan with parchment paper, leaving an overhang so the loaf can be easily lifted out once baked.
  • In the bowl of a stand mixer, cream together the softened butter, vegetable oil, and sugar on medium-high speed for around 4 minutes, until pale in colour and fluffy. Scrape down the sides of the bowl as needed. 115 g unsalted butter, 30 g vegetable oil, 200 g granulated sugar
  • Add the eggs one at a time, mixing well after each addition, followed by the vanilla. 3 large eggs, 1 tsp vanilla paste
  • Whisk in the sourdough discard and yoghurt until smooth. If the mixture looks split or grainy at this stage, blend briefly with an immersion blender to bring it back into a smooth emulsion. 100 g sourdough discard, 120 g natural yoghurt
  • In a separate bowl, whisk together the flour, baking powder, baking soda, and salt. 220 g all-purpose flour, 1 tsp baking powder, 1/2 tsp baking soda, 1/2 tsp salt
  • Fold the dry ingredients into the wet, alternating with the milk in two additions, starting and ending with the dry. Mix until just combined. 80 g whole milk

Chocolate swirl

  • Heat the milk until steaming hot, then stir in the cocoa powder, sugar and espresso powder until it makes a smooth, thick paste. 30 g whole milk, 25 g cocoa powder, 25 g granulated sugar, 1 tsp instant espresso powder
  • Stir a couple of tablespoons of the cake batter into the cooled cocoa paste to loosen it, then transfer just under half of the cake batter into the cocoa mixture and fold gently until evenly combined.
  • Spoon alternating dollops of the vanilla and chocolate batter into the prepared pan. Use a butter knife or skewer to gently swirl the two together with a figure eight motion. Don't overdo it or you'll lose the swirl effect.
  • If baking right away, preheat the oven to 350°F (180°C) while you finish swirling. If cold-fermenting, cover the pan tightly and place in the fridge overnight (see notes).
  • Bake for 55 to 65 minutes, until a skewer inserted into the centre comes out clean and the internal temperature reads around 200°F (95°C). Tent loosely with foil after 40 minutes if the top is browning too quickly.
  • Let cool in the pan for 15 minutes, then lift out using the parchment overhang and place on a wire rack to cool completely.

Notes

Both US customary and metric measurements are provided. Use the toggle to switch between the two.
Cold-fermenting (optional): Cover the pan tightly and place it in the refrigerator for 8 to 16 hours. Cold fermenting allows the flour to absorb more moisture from the batter, leading to a more tender and moist crumb. The batter can be baked straight from the fridge, no need to bring it to room temperature first. Add an extra 5 to 10 minutes to the bake time.
If the batter splits: If your sourdough discard or yoghurt is too cold when added, the creamed butter mixture can curdle and look broken or grainy. An immersion blender will bring it back into a smooth emulsion in a few seconds. To prevent this, take the discard and yoghurt out of the fridge an hour before baking.
Sourdough discard: Unfed discard works best as it's more acidic, which reacts with the baking soda and adds a subtle tang. An active starter will work too, but the texture may be slightly different.
Blooming the cocoa: Heating the milk before adding it to the cocoa powder dissolves the cocoa solids and releases its aromatic compounds, which deepens the chocolate flavour. A teaspoon of instant espresso powder added at this stage intensifies the chocolate without making the cake taste of coffee.
Cocoa powder: Either natural or Dutch-processed cocoa works in this recipe. Natural cocoa gives a brighter chocolate flavour and a slightly better rise. Dutch-processed gives a darker, more dramatic swirl with a smoother, more mellow chocolate flavour. Use whichever you prefer.
Yoghurt substitute: Buttermilk or sour cream work as a 1:1 swap for the yoghurt. Both bring acidity and tenderness in the same way.
Storage: Store at room temperature in an airtight container for up to 4 days, or wrap and freeze for up to 3 months.

Nutrition

Serving: 1sliceCalories: 301kcalCarbohydrates: 45gProtein: 6gFat: 12gSaturated Fat: 7gPolyunsaturated Fat: 1gMonounsaturated Fat: 3gTrans Fat: 0.4gCholesterol: 82mgSodium: 251mgPotassium: 136mgFiber: 2gSugar: 24gVitamin A: 387IUVitamin C: 0.1mgCalcium: 79mgIron: 2mg
Keyword marble loaf cake, sourdough chocolate vanilla cake, sourdough discard cake, sourdough discard marble cake, sourdough marble cake
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