Best Moist Gluten-Free Chocolate Sheet Cake
The BEST gluten-free chocolate cake recipe, bar none. With a thick swirl of chocolate buttercream and festive sprinkles, this is the perfect gluten-free chocolate birthday cake. Bake as cupcakes or a layer cake!
- Prep time
- 20 min
- Cook time
- 50 min
- Yield
- 24 servings
- Difficulty
- HARD
Ingredients
Quantities are shown as originally provided.
- Scant 1 cup milk (1 cup minus 1 tablespoon) ( or equivalent in buttermilk and skip the vinegar)
- 1 tablespoon white vinegar
- 168 g sweet rice flour (also called Mochiko - different from "white rice flour" or "brown rice flour")
- 99 g gluten-free oat flour
- 84 g millet flour
- 128 g unsweetened Dutch-processed cocoa powder (sifted (I use Rodelle Organic Cocoa))
- 503 g granulated sugar
- 2¼ teaspoons baking powder
- ¾ teaspoons baking soda
- 1½ teaspoon kosher salt
- 3 large eggs (room temperature (see vegan option below))
- 4½ tablespoons neutral vegetable oil (such as safflower, sunflower, or canola oil)
- 1½ teaspoon pure vanilla extract
- ¾ teaspoon chocolate extract (or ¾ teaspoon more vanilla extract (I use Rodelle chocolate extract))
- 1 cup hot water
- 1½ cups unsalted butter (just about room temperature 60-70°F)
- 4½ cups powdered sugar
- ¾ cup unsweetened Dutch-processed cocoa powder ( sifted)
- ½ teaspoon kosher salt
- 2½ teaspoons pure vanilla extract
- ¾ teaspoon chocolate extract (or ¾ teaspoon more vanilla extract)
- 3-4 tablespoons whole milk or heavy cream (dairy or non-dairy)
- Optional: Festive sprinkles
Instructions
- 1
Preheat the oven to 350°F. Prepare a 9x13 cake pan by lightly oiling it, and lining it with parchment paper. See notes for converting to cupcakes or a layer cake.
- 2
If not using buttermilk, combine the milk and vinegar in a small cup and let sit while you measure the flour, at least 5 minutes.
- 3
In a large bowl, sift together the sweet rice flour, oat flour, millet flour, cocoa powder, sugar, baking powder, baking soda, and salt.
- 4
In the measuring cup, whisk the milk and vinegar mixture with the egg, oil, vanilla extract, and chocolate extract until smooth. Pour this mixture into the dry ingredients and stir lightly. Pour the hot water into the dry ingredients and mix until completely smooth, scraping up the sides and bottom to completely incorporate.
- 5
Pour the batter into the prepared cake pan and bake for about 45-55 minutes, or until a toothpick inserted in the center comes out clean or with just a few moist crumbs and the center bounces back when poked. In my experience, it's best to err on the side of an extra minute or two to be sure - this cake is very moist and won't over-bake very easily.
- 6
Let cool in the pan for 10 minutes, then overturn the cake onto a wire rack to cool completely. To do this, I place a large sheet pan over the baking pan and, holding it together, carefully flip the cake to release. Peel off the parchment paper, then place a wire rack over the top, and carefully flip right side up.
- 7
While the cake cools completely, prepare the frosting. In the bowl of a stand mixer fitted with the paddle attachment, cream the butter over medium speed.
- 8
Sift together the powdered sugar, cocoa powder, and salt. Slowly add this to the butter, in 4 batches, beating until incorporated. Add the vanilla and chocolate extracts and mix until smooth. Add the milk or cream, starting with just 2 tablespoons and adding additional milk or cream as needed, until frosting is smooth and spreadable. It should be somewhat glossy, but still hold swirls.
- 9
When the cake has cooled, swirl the buttercream over the top of the cake (I recommend using the back of a soup spoon) and top with colorful sprinkles, if desired. Slice into 24 pieces and devour.