Buttermilk Chocolate Sheet Cake
servings12 slices
This Buttermilk Chocolate Sheet Cake is soft, deep in flavor, and covered in a smooth cocoa frosting.
Video
Ingredients
For the cake
- 1 ⅓ cups (160 g) all-purpose flour (plain flour)
- 1 cup (200 g) white granulated sugar
- ⅓ cup (35 g) unsweetened cocoa powder, sifted
- ¾ teaspoon baking soda (use a ¼ teaspoon three times, level each one, too much affects taste and texture)
- ¼ teaspoon salt
- ⅔ cup (160 ml) buttermilk
- ½ cups (120 ml) oil (canola, sunflower, or vegetable)
- 1 large egg, beaten
- 1 teaspoon vanilla extract
- ⅔ cup (160 ml) hot coffee or hot water (around 175°F / 80°C, not boiling)
For the frosting
- 1 ½ cups (180 g) powdered sugar (icing sugar), sifted
- ⅓ cup (40 g) unsweetened cocoa powder, sifted
- ⅓ cup (85 g) unsalted butter, melted and hot
- ¼ cup (60 ml) buttermilk, at room temperature
Instructions
- Lightly grease a 9×13-inch metal baking pan (quarter sheet) 33 × 23 cm) and line just the bottom with parchment.
- Preheat the oven to 350°F (175°C) or 160°C fan.
Make the cake
- In a large bowl, whisk together the flour, sugar, sifted cocoa powder, baking soda, and salt.
- Add the buttermilk, oil, beaten egg, and vanilla extract. Whisk just until combined.
- Pour in the hot coffee or hot water Tip: If using instant coffee, dissolve the granules in the hot water before adding
- Whisk until the batter is fully combined. It will be liquidy.
- Bake: Pour into the prepared pan. Bake for 18–22 minutes, or until a skewer inserted in the center comes out clean.
- Cool: Leave the cake to cool completely in the pan.Tip: Don’t lift or turn out the cake, it’s soft and can break. It cools to a light texture right in the pan.
Make the frosting
- Tip: Only make the frosting once the cake is completely cool and you're ready to use it. It sets quickly and won’t spread well if made too early.
- In a bowl, sift the powdered sugar and cocoa powder. Tip: Skipping this step can leave clumps that won’t smooth out.
- Pour in the hot melted butter, and buttermilk.
- Whisk until smooth and glossy. The frosting may look thick at first, but keep mixing, it turns smooth and spreadable quickly.
- Spread evenly over the cooled cake with a spatula.Optional: Use a decorating comb to make a wave or line pattern. See video above for technique.
Recipe Notes
Baking soda: Also known as bicarbonate of soda (UK). Use a ¼ teaspoon three times and level each one carefully. Avoid heaping or guessing — too much baking soda can affect the taste and texture.
Nutrition
Serving: 1slice | Calories: 349kcal | Carbohydrates: 51g | Protein: 4g | Fat: 16g | Saturated Fat: 5g | Polyunsaturated Fat: 3g | Monounsaturated Fat: 8g | Trans Fat: 0.2g | Cholesterol: 31mg | Sodium: 145mg | Potassium: 121mg | Fiber: 2g | Sugar: 37g | Calcium: 34mg | Iron: 1mg
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